One Rep Max Calculator

By | February 11, 2004
one-rep-max calculator
This calculator will estimate your one rep maximum based on weight and repetitions.

It will also estimate 5, 10, and 15 rep maxes based on the one rep max that was computed for hypertrophy-specific training (HST).

What Is a One Rep Max?

One rep max is the amount of weight you can lift for a given exercise one time only. It is a great indicator of strength and, in some cases, fitness level.

However, performing a one rep max can be dangerous. It is recommended that you use a safer method, such as finding out how much weight you can lift for, say, 10 repetitions. This equation will convert that weight into your one rep max.

Enter number of reps performed:
Enter weight used:
One rep max (formula one)

weight / ( 1.0278 – ( 0.0278 * reps ))
One rep max (formula two)

weight * ( reps * 0.033 + 1 )
5-rep max
10-rep max
15-rep max

More Calculators

How to Improve Your One Rep Max

There are a number of systems available. To improve your bench press, see this guide.

Speed and strength are related because speed requires force output. Power-lifting, even though achieving a one-rep maximum appears to be slow, is considered “explosive” due to the forces generated.

Finding Your Other Maximum Weights

one rep maxThe calculator also estimates 5, 10, and 15 rep maxes. These should only serve as starting points. There are numerous factors that contribute to your ability to achieve a given load at a particular repetition range.

Those with local muscular endurance may be able to lift heavy loads for high repetitions, while others may find their 15-rep max’s are much lower than the calculator reports due to the fact that their muscles exhaust much earlier.

Keep a Journal

Always keep a detailed training journal and adjust to what you are actually able to lift during a workout (for this reason, I always consider my first new workout a learning session, where I hone in on the appropriate weight ranges based on how the workout progresses).

This is a great way to track how your one rep max is progressing and provides great motivation for making gains.

26 thoughts on “One Rep Max Calculator

  1. David

    I think this rep max calculator is pretty accurate, I use it all the time, but what about finding a 5×5 max? It says I can do 189 lbs 5 times, which may be right, but I would not be able to do that for 5 sets.

  2. jesse

    Why is it that when you input a large number of reps the calculation is so far out of line. 135 for 35 reps for instance gives a 1 rep max of 2464 pounds. Obviously not the accurate number.

    1. Ted

      Hi Jesse, It’s because there is a rep cap. A body builder wouldn’t do 35 reps of 135 pounds so 35 throws the calculation out of whack. It only works with when normal reps are used which is usually no more than 12.

      1. Cody

        Actually at home all I have is 100 lbs to lift so I end up doing it 50 to 60 times for each workout

        1. Ted

          There lies a problem, you’ll really need to get more weights or join a gym bud.

  3. Chris Paladino

    What is the actual formula for getting a 10 and 15 Rep Maximum?

    1. admin

      Chris, it’s basically the one-rep amount multiplied like this:

      tenrepmax = onerepmax * ( 1.0278 – (0.0278 * 10))

  4. Jeff Frazier

    Why have two one rep max calculators?
    Which calculator is more accurate?
    Is this just to give us a range for our potential max?

    1. Ted

      Hey Jeff, Yeah this just gives you a point of reference. No calculation could factor in all the variables in a real world situation and be 100% accurate. Which one did you find to be the most accurate when you tested it at the gym?

  5. john johnso

    hello its is broken for me i can do 20 pounds 102 times….. what will that actually be?????

    1. Ted

      Hi John, It’s not broken, it’s just that your pounds and reps are outside the parameters. You need to put in a weight that you can do 10 times.

  6. bryce

    uhhh dont mean this in a mean way but i think your calc is incorrect i do 50lbs 10 reps for my normal work out but i can bench 170……

    1. Ted

      I don’t think your understanding this obviously you can do more than 50 pounds 10 times, right?

  7. Stephen

    This is awesome. I haven’t maxed out since I was in HS and have no clue what my current maxes are.

    I’m currently on Starting Strength and that program is based on 3 sets of 5. I’m at 105 on bench now, but I have not stalled yet so this will be handy to get an idea of what my IRM is when I start having trouble.

  8. Don

    I think the calculator is a great and safe way to calculate a one max rep.

    It never seems to amaze me how some people try to over complicate everything instead of just excepting things for what they are.

  9. nik

    Do I use the weight for my best one set, or the weight I work out with normally for 3 sets?

  10. Bijan

    The second formula works best for me… 4 x 365 deep squats = 414 here and I 1RM 415.

  11. Ryan

    At my school, I completed 35 reps with 225 pounds. (squats)
    It says that my one rep max is 485 pounds. Can I trust that? I can’t see my body being able to hold that up without collapsing. Also, how would my school measure the school records? Would it be with one repetition or with as many as I can with a lower weight?

  12. pete

    I can bench 230×15 the calc says I can max at almost 400lbs I wont try over 315 out of fear of a ripping my pec major again, should I believe this? also I only weigh 192lbs so I’m not the biggest guy that’s why its hard for me to trust the calculation.

  13. เล่นกล้าม

    Great calculate program. thank a lot.

Comments are closed.