Free tool · Training
One rep max (1RM) calculator
Short answer
Your one-rep max (1RM) is the heaviest weight you can lift once with good form. You can estimate it from a harder set of up to 10 reps. Lifting 100 kg for 5 reps gives an estimated 1RM of 116.7 kg with Epley's equation and 112.5 kg with Brzycki's. Sets of 10 reps or fewer work best.
Last reviewed 26 October 20262 published sourcesNot medical advice
Reps keeps track of this for you on iPhone, iPad and Apple Watch.
Get Reps freeOne rep max calculator
Use a recent set taken close to failure.
Enter the weight and reps from a hard set to see your estimated 1RM.
Runs entirely in your browser. Nothing you type is saved or sent anywhere.
The equations
Epley: 1RM = weight × (1 + 0.0333 × reps), as given by LeSuer et al. (LeSuer et al., 1997). A single rep is already your 1RM, so the calculator returns the weight itself for one rep.
Brzycki: 1RM = weight ÷ (1.0278 − 0.0278 × reps). Brzycki designed it for sets of 10 or fewer repetitions to fatigue (Brzycki, 1993).
Both assume the set went to, or very near, failure. Stopping with reps in reserve makes the estimate too low.
| Reps | Epley | Brzycki |
|---|---|---|
| 1 | 100.0% | 100.0% |
| 2 | 93.8% | 97.2% |
| 3 | 90.9% | 94.4% |
| 4 | 88.2% | 91.7% |
| 5 | 85.7% | 88.9% |
| 6 | 83.3% | 86.1% |
| 7 | 81.1% | 83.3% |
| 8 | 79.0% | 80.5% |
| 9 | 76.9% | 77.8% |
| 10 | 75.0% | 75.0% |
Getting a good estimate
Use a recent set taken close to failure with consistent technique, and enter the weight in whatever unit you lifted; the estimate comes back in the same unit. The two equations agree exactly at one rep and give slightly different answers in between, so the calculator also shows their average.
Building strength over weeks? Keep an eye on how quickly your total training load rises with the ACWR calculator, and make sure protein keeps up with the protein calculator.
Log the set, race your best
Say the weight and reps out loud mid-set and Reps logs it, then shows a ghost of your previous best so you know when you are ahead.
Free to download · iPhone, iPad and Apple Watch
Common questions
Which 1RM formula is most accurate?
No single equation is right for every lift and every lifter. LeSuer et al. (1997) tested published equations, Epley's among them, against measured 1RM in the bench press, squat and deadlift. Brzycki designed his for sets of 10 reps or fewer, which is why this calculator caps the set at 10 and shows both equations side by side.
Is it safe to test a true one-rep max?
A true max is an all-out effort with a real chance of a failed rep. Estimating from a hard set of up to 10 reps avoids lifting a maximal single. If you do test one, use a spotter or safety arms.
How do I use my 1RM for training?
Most programmes prescribe loads as a percentage of 1RM. The table on this page inverts both equations to show roughly what you could lift for 1 to 10 reps. Retest every few weeks, because your 1RM should change as you train.
Sources
Figures on this page were checked against these publications on 26 October 2026.
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance. 1993;64(1):88–90. doi.org/10.1080/07303084.1993.10606684
- LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research. 1997;11(4):211–213. doi.org/10.1519/1533-4287(1997)011<0211:TAOPEF>2.3.CO;2
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