Climbing Critical Force Calculator

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Critical Force Calculator

The Critical Force Calculator will help you determine where you stand with your forearm aerobic endurance. If you’re a strong sport’s or trad climber, but end up pumped on your way to the crux, it means that your forearm aerobic endurance likely requires some attention. The Critical Force Calculator will also allow you to find the optimum load at which you should train so that you will soon breeze up through those endurance routes! 

The calculator provides a basic assessment of your climbing endurance level. If you would like to get a detailed personal climbing performance evaluation like this one, just send your input numbers to me directly at [email protected], and I’ll get back to you with an in-depth lead climbing level evaluation. I will analyze your current performance and give you hints on what to train to quickly improve your climbing!

For best results, train exactly at CF intensity and try to maximize the total work done.


To determine your forearm aerobic endurance Critical Force, you can use the calculator below. Input your body weight and your 7-second MVC on a 20 mm edge, followed by respective times to failure for the 7/3 Endurance Repeaters at 80% MVC-7 and 60% MVC-7. For the last measurement you may choose 45%, 50% or 55% MVC-7 load, just make sure that you fail in under 1200 seconds. 

The calculator will output your CF and the weight you need to subtract in order to exercise exactly at CF load. You will also receive a brief assessment of your strength and forearm aerobic endurance. The calculator is calibrated for the half crimp grip on a 20 mm edge, to enable a direct comparison with the results published in [1]. The bouldering level prediction is based on the results of the survey published at [2].

You can find more detailed information regarding the role of the Critical Force in sport’s and climbing endurance training in [3].

Example Critical Force test

Let’s say you weigh 68 kg, and you take the MVC-7 test on a 20 mm edge. You can add 32 kg to the bodyweight and hang for 7 seconds, so the MVC-7 load is 100 kg. Now we can calculate your 80%, 60% and 45% loads, which are 80 kg, 60 kg and 45 kg respectively.

  1. Test your T80% :
    • To set the 80% load, you must add 12 kg to the harness.
    • Execute a set of 7/3 Repeaters until failure.
    • Add the hanging times together. This means that if you were able to execute 10 full hangs and failed at hang 11 in the 4-th second, then your T80% is 74 seconds.
    • Rest 15 minutes before the next test.
  2. Test your T60%
    • To set the 60% load, you must remove 8 kg using a pulley system.
    • Execute a set of 7/3 Repeaters until failure.
    • Add the hanging times together. This means that if you were able to execute 15 full hangs and failed at hang 16 in the 4-th second, then your T60% is 109 seconds.
    • Rest 30 minutes before the next test.
  3. Test your T45%:
    • To set the 45% load, you must remove 23 kg using a pulley system.
    • Execute a set of 7/3 Repeaters until failure.
    • Add the hanging times together. This means that if you were able to execute 60 full hangs and failed at hang 61 in the 4-th second, then your T45% is 424 seconds.
    • If your aerobic endurance is very good, and you are able to last more than 20 minutes at the 45% load, you should change the load to 50% or even 55% of your MVC-7 and redo the test.
  4. Enter your data into the form and press calculate.
kg lbs
T(45%) [s]
T(50%) [s]
T(55%) [s]


The idea of Critical Force

Critical Speed (CS) and Critical Power (CP) are well-known concepts used in sports training. Imagine yourself walking at about 6 km/h – you could probably carry on like this for hours. On the other hand, unless you’re an elite marathon runner, you probably couldn’t run at 20 km/h for very long. This means that your running critical speed, which is the speed at which you could theoretically run for an unlimited time, lies somewhere between 6 – 20 km/h. Cycling coaches use the term Critical Power, which defines the power output, at which you could cycle for hours. For climbing, the term Critical Force (CF) is more relevant, meaning the maximum load at which you should be able to climb indefinitely without falling off.

The Critical Force determines the performance on endurance routes, and it is directly related to the forearm aerobic capacity. Critical Force is usually expressed as a percentage of the climber’s body weight, or their maximum voluntary contraction (MVC). For elite sport climbers, it could reach up to 60% of their MVC, while for boulderers and poorly conditioned route climbers, it could be below 30% MVC. Knowing your CF is important because it was shown that aerobic capacity is trained most efficiently exactly at critical loads [4].


  1. Giles, D., Chidley, J.B., Taylor, N., Torr, O., Hadley, J., Randall, T., Fryer, S., 2019. The Determination of Finger-Flexor Critical Force in Rock Climbers. International Journal of Sports Physiology and Performance 1–8. (link)
  2. (link)
  3. J. Banaszczyk, StrengthClimbing – Endurance Repeaters, May 2, 2019. (link)
  4. McGawley, K., 2010. The application of the critical power construct to endurance exercise. University of Brighton. Student thesis: Doctoral Thesis. (link)
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31 thoughts on “Climbing Critical Force Calculator”

    1. Hi Tom! Thanks for the question! Every time you execute a hang that’s close to your limit, you burn phosphocreatine (PCr), which is used to produce ATP that fuels your muscles. It takes between 3 – 5 minutes to replenish the PCr stores after such a maximum effort completely. The longer you hang, the more you deplete PCr, and the longer you need to rest. So, for example, after a single MVC-7 attempt, it might be enough to rest 3 minutes, but after a 30-second hang, it possible that you would have to rest even 10 minutes to recover fully.
      To determine the MVC-7 with reasonable accuracy, you need to perform at least 3 – 4 hangs, and the fatigue might start to accumulate, even if you rest for 5 minutes after each hang. To stay on the safe side, I think it’s better to wait 10 – 15 minutes after the MVC-7 tests and before moving on to the 80% Repeaters.

  1. My results are as follows:
    Mvc-7 115kg. (60kg bw +55kg)
    T80 = 23s
    T60 = 91s
    T50 = 112s
    I used to just be able to hang 50kg at a push, but the 55kg felt ok, and i failed at the 6th second for 60kg.

    1. Hi Tom!
      Thanks for posting your results! First of all, I need to congratulate you on your finger strength! At 55 kg added weight, you probably boulder around V11 🙂
      I took a closer look at the results of your Critical Force test. My guess is that you did the 50% test because, at 45% MVC, you were able to make it past the 20-minute mark, am I right? I plotted your results on the graph below.
      The green line is a typical characteristic measured for one of the climbers who follow my training plan. The person is a typical route climber, with a pretty decent CF score of 49% MVC-7.
      The red squares are your measured results, and the blue line is the endurance curve calculated for your measured T50%. The T50% result lies below the curve, which means that the result is too low – it does not fit the theoretical model. It should be around 190 seconds.
      The gray dashed line is the endurance curve, calculated assuming that your T45% result was 840 seconds, which is equivalent to completing full 20 minutes of the exercise. The curve is almost the same as the curve plotted using T50%. This confirms that your measured T50% result is too low.
      The T60% measurement seems just right, and the T80% measurement seems also slightly low – it should be at least 40 seconds.
      To sum up, it looks like you were still tired from the MVC-7 measurements when you did the 80% measurement. Then you took a good rest and measured T60% correctly, and then you were tired again when doing T50%. Perhaps you measured after testing for T45% first.
      Still, it’s obvious that you are a very strong boulderer and sport climber. Based on your results, I believe that you should be able to project in the 8b – 8b+ range. But there is certainly room for improvement when it comes to your endurance. If you could increase your CF from 45% MVC-7 to 50% MVC-7, which is common among sport climbers, you could make big progress.
      Anyway, I hope this helped.

  2. I am definitely an outlier. I just took the rest times that were given in the example. I also didnt try the t45 just because i had the right weight for t50. I was curious that my times were much much lower than the given examples. I have been sportclimbing 20 years and never really bouldered, the hardest i climbed was 5.13c/14a and maybe a small amount in the 5.13 range. My max hang used to be +50kg but i tried a different training tool and managed to surpass it. Im continuing to use it to make sure it is what is increasing my finger strength.

  3. I have retested the hangs on a different well known 20mm rung with rest days between attempts. Mvc-7 =110kg
    T80 = 55s. T60 = 98s T45 = 230s.
    With the calculated adjustment, is that designed to be used when doing a repeater form of hangboarding?

    1. Hi Tom!
      Thanks for the input! Yes, the calculated adjustment tells you how much weight you need to subtract from your body weight to perform 7/3 Endurance Repeaters exactly at Critical Force load. Training at CF load was found to be the most efficient way of improving endurance. At this load, you should be theoretically able to perform 7/3 Endurance Repeaters for at least 20 minutes (840 seconds TUT), but in my experience, it takes climbers at least a couple of sessions before they reach the 20-minute mark. You may also divide the Endurance Repeaters into various patterns, like 1 minute of exercise and 1 minute of rest, and repeat this 10 – 20 times. I found this training to be extremely effective in improving both the aerobic and anaerobic endurance.

  4. Hi jedrzej.
    I tried training at cf load and managed sets of 15 repeaters before having to stop to rest. I then repeated this until i managed to do all 120 reps, the equivalent of 840s TUT. Ive yet to do it for a decent time to see results, but it is very pumpy.
    Earlier you mentioned increasing cf from 45 to 50% mvc-7. To do this do you train at cf load until you can complete the 20min of repeaters with no rest, and then reduce the cf load slightly or recalculate the whole thing, ie mvc-7,t80,t60,t45, or does it involve strength gains and trying to improve your mvc-7? Thanks for your time.

  5. Hello there, you have created very interesting resource here. I have just finished 60% 9 weeks of my base training. Just to give extra info. I have another 6 weeks left of it.

    My results are:
    MVC7 109kg(Body weight 68kg + 41kg)
    T80: 90s
    T60: 139s
    T50: 349s it felt like it is not going to end then – boom.

    1. Hi!
      Thanks! I’m trying my best! Based on your results, I did a little rough assessment. Your level seems to be about 8a+, I think. It looks like you’re a versatile climber with a good balance between strength and endurance. I believe that in order to progress you need to develop both facets, but I think focusing more on finger strength should help you quickly reach the next level. Anyway, I hope this helps. If you need a training program, don’t hesitate to let me know!

  6. Hi Jędrzej,

    Thanks for your work and reply. My boulder grade is 8A and the lead is 8a+ you are right.

    I have noticed that roughly after 4 months block of training I get the best adaptations from strength/power training. No surprise as that is the biological adaptation period.

    Last couple of years I took too much time off from training in Summers and just climbed lots. Over the next year I will try not to have longer than 2 week performance period for roped climbing. Then back to base training. I hope I will be getting to the next level. It seems that when I was climbing whole summer, after I need to do a lot of catching up in the strength department.


  7. Great website.
    Is Critical Force another term for what some people call ‘anaerobic threshold’ or ‘lactate threshold’? (Although depending on who you’re talking to anaerobic threshold and lactate threshold are not necessarily synonymous)

    1. Hi Malcolm!
      Thanks a lot! As you wrote, there is some confusion around the nomenclature here. I addressed a similar question in an earlier comment. Please have a look here. According to the definitions in the Ph.D. thesis of Kerry McGawley, Critical Force lies above the lactic threshold and also above the MLSS.

  8. Hi what is good time on 60%?
    My test is
    MVC-7 50kg BW=68kg on 17mm all in all 118kg

    1. Hi Marco!

      173% BW on a 17 mm edge? Wow, that’s very strong! However, endurance at 60% MVC-7 is a relative value, so it’s independent of the edge depth, and we can have a general analysis. An excellent result would be anything above 200 seconds TUT, so roughly 280 seconds T_total. Yours is decent (if we’re talking TUT). If you want a detailed analysis of your endurance profile, please let me know in an email.


  9. Hi Jędrzej
    First of all, great website, great idea to publish so much knowledge. I started last December with my serious hang board training, using the zlagboard. I did some research as well and find out that it is important to grow the force you bring in your training. I had the simple idea to do 7/3 repeaters always till I fall off. This I do 3 times per training day. First with 90% BW an 100%BW. If I could do more than 4-5 minutes I went to a higher BW percentage or from 20mm to a 12mm hold. This week I found your website and start too study it. Find out I have the similar data that you measure.
    Here are my results
    13 Dez 2020 : MVC7 max 150% BW, 90%BW 54sec, 100%BW 59sec, 120%BW,
    Mar 2021: MVC7max 164%BW, 90%BW 1200sec, 100% BW 660sec, 120%BW 290sec, 135% BW 90sec
    My hardest boulder 7a (not really a boulder guy)
    My hardest sport rout 7c+ (what I always do)
    Body 59kg 160cm

    May I get it wrong but on some part of the website your “100%” point is the MVC7, on other part is your ”100%” point the BW. From this point you start to calculate your curve. I guess the 100 BW should be the “100%” point. Because your bodyweight is the only “constant” what you “can’t” change. For example, if you start January at BW 60kg and your MVC7 is 80kg and CF 40kg and after a month max force training (February) your MVC7 will rise 10kg to 90kg. the CF is sill 40kg your endurance is now lower because you lift your “100%” point, but in reality your endurance is the same as a month ago.

    I would love to share my data’s with you, I use it all in google sheets.
    Cheers Daniel

    1. Hi Daniel!
      Thank you for your comment! It’s exciting to know that others are also exploring the idea of Critical Force! I think that the knowledge related to climbing training is growing fast in recent years within the community, and I believe that we can all contribute – keep it up!

      Regarding the CF measurements, it’s helpful to know both the relationship with your BW and with your MVC-7. Measuring CF against your BW is indeed what matters the most. However, measuring against your MVC-7 gives you valuable insight into your endurance profile.

      Coming back to our example, if you improve your MVC-7 is 80 kg, and your CF is 40 kg, then the ratio is 50%, which is an excellent result for a sport climber. At 133% MVC-7/BW, the climber is not very strong but can maintain a decent amount of strength for a very long time. Once the climber improves the MVC-7 to 90 kg and the CF stays at 40 kg, the MVC-7 becomes 150%, which is decent, and the CF becomes 44%. That’s still a pretty good result regarding endurance, but the climber’s profile changes to a more powerful athlete, capable of climbing cruxy and bouldery routes. For boulderers, it’s not uncommon to have the CF/MVC-7 relationship as low as 25 – 30%, but it could still be quite high relative to their BW if they’re strong.

      Training for sport climbing is tricky because you want to develop both strength and endurance, and the two often get in the way of each other. There are a lot of useful routines and training programs to develop concurrently. Some drills focus on the anaerobic system and help build strength (like 7/3 Repeaters at 80% MVC-7), and some target the aerobic system and may be detrimental to strength and contact force. It’s good to cycle through them and mix things up to avoid hitting a plateau.

      Sure, you can share your data with me through google sheets. I promise to take a look.

  10. Hi i did that test,what i suppose to climb?
    My bodyweight is around 66-70 my MVC-7 is( BW 67+65kg)
    80% 78s
    50% 287s
    I also test my weighted pull up and my 1 rm is 55kg
    Great website,awesome test!

    1. Hi Alex!
      I’m glad you like the site, thanks! It looks like you’re a pretty strong climber. Your average redpoint level should be around 8b+, but could be more if the route fits your style. It seems that you still have a big potential to improve your endurance, so work on that and you’ll be golden!

  11. I finally made it to this test and my results are :
    Mvc-7 : 118kg. (83kg+35kg)
    T80 = 63 sec
    T60 = 112sec
    T45 = 196sec

    So the calculator says i have pretty poor aerobic endurance wich is what i know is my weakest link…what would be a route grade with these stats?

    thx for that:)

    1. Hi Rene!

      Yes, it does look like your aerobic capacity is a bit on the low side, but your strength endurance is pretty ok. Maybe you didn’t recover from the previous tests? I always recommend to do the final test in a separate session.

      In any case, it looks like you could manage a technical, vertical 7b/+, but I think you might struggle with steeper routes, which give you little chance to rest, unless they’re short. If you need a more detailed analysis, you can always write me an email.

      1. Hi,i just remembered to have a look if you‘d answered and want to give some feedback.Your Analysis pretty on point,my main project is a vertical techy 7b+ ,on steeper terrain i‘m having a hard time goin over 7a/+.
        Thx and greets

  12. Hello!
    First of all, thanks a lot of the work and science your adding to the climbing community!
    1- What is the formula to calculate the critical force? and to reproduce the graph?
    2- To know the CF progress over 4 weeks for example, we should retest the MVC-7 right? Because I assume that progressing in CF % means endurance dominant macrocycle and loss of MVC-7, unless MVC-7 is maintained by doing 1 session a week of maxhangs or finger strenght work.
    3- If CF is really the maximum power we can maintain from the aerobic endurance system, we should be able to maintain it for much more than 20 min no?
    4- My results were :
    MVC-7: 115KG, MY WEIGHT IS 73KG
    T80: 83sec
    T60: 135 sec ( it was more like T57 because the friction of the carabineer used as a pulley was 50 % of the 3.75kg I wanted to take off of my weight…)
    T45: 355 sec
    I’ve been climbing for 2 years and want to get to the elite level: 8c-9a in sport climbing. I actually didn’t project anything outside so my max grade is 7c sport, 7b+ onsight and 7a flash bouldering.
    Thanks again

    1. Hi Yann, thank you for the comment! I will try to address your questions one by one:

      1- You can find the exact formula in the cited paper by the guys from Lattice training. If you go to Researchgate, they even have the excel spreadsheet with the formulas implemented to calculate the CF (link). To make the plots, you need to calculate the function for every time instant in excel.

      2- Yes, you need to retest MVC-7 eventually. I typically know mine because I combine MaxHangs with endurance Repeaters. I suppose it’s enough to do the full test every 12 weeks or so. If it’s a dominant endurance macrocycle, you’re indeed likely to lose some strength. I usually manage to progress both at the same time, albeit perhaps at a slower rate.

      3- In reality, at these loads, there is still a strong anaerobic component present. That’s why you can last only 20 minutes or less. Anyway, 20-minute CF is just a metric. You can have 5-minute CF, 10-minute CF, or 30-minute CF just as well. At 20 minutes, you’re striking a good balance between the anaerobic and aerobic components, which makes the test meaningful.

      4- The times you provided are Time Under Tension (number of reps*7 seconds + plus the duration of the last failed rep) or the Total exercise time? I want to make sure to give you the right level prediction.

      You’re perfectly right about the bigger edges. I actually believe that it’s better to train on a 30 mm edge unless you’re aiming for routes with small holds.

  13. Hey JĘDRZEJ!
    Thank you for taking the time to answer all my questions!
    For question 4, yes it’s Time under Tension + duration of the last failed rep.
    Thanks again

    1. Hi Yann!
      Based on your finger strength and endurance, it looks like you’re a versatile climber and your sport redpoint level should be around 7c+ already. However, you need to address both strength and endurance if you want to break into higher grades. Fortunately, it looks like you still have some potential to work with. Please let me know if you need a more detailed analysis.

      1. Hello!
        Thank you!
        Yes your prediction is accurate, I’ve been onsighting 7a+ and 7b regularly and so projecting on 7c+ should be realistic.
        If you have the time of course I would like to have more details of the analysis.
        Also my goal is to not climb 4-5times a week outdoors so I should be including strenght trainings on the same days (early mornings), would you recommend doing a reduced amount of steve betchel ladders to improve strenght on the long term (twice a week)?

        Thanks a lot!


        1. I think you meant that your goal is to climb 4 – 5 days outdoors? Is that correct? In any case, that’s a tremendous amount of climbing in itself – I don’t think that adding additional hangboard sessions in the morning is a good idea. Unless you’re a professional athlete training with a coach.

          For an amateur climber, the optimum volume would be 3 – 4 training days per week. That could mean three days of climbing + one hangboard session or two days of climbing supplemented with two hangboard sessions.

          If done by the book (three hold positions per session), Bechtel’s Ladders are a surprisingly high-volume training routine, so if you’re going to pair that with a lot of climbing, you should indeed consider doing a reduced protocol.

        2. Adrian Huttenberger

          Back from from a climbing weekend with tired muscles, i did the test today.
          MVC7 132kg (66kg + 66kg)
          T80 27sec
          T60 175sec
          T50 255sec
          Guess the low T50 is much related to the climbs on the weekend.
          What to improve best? Apart from all 🙂

          1. Hi Adrian!

            Your T60 and T50 are fairly normal. However, it’s your T80 that’s way below average and may have been influenced by either the MVC-7 measurements (very good result by the way), or by your weekend climbing. I suggest that you retry the endurance tests, the T80 in particular when you’re fully recovered. I will then be able to answer your question.

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