One Rep Max (1RM) Calculator

Enter the weight and the number of clean reps you managed to failure. The calculator estimates your 1RM – the load for exactly one repetition – with two widely used formulas.

Unit

Weight lifted

Repetitions

reps

Most reliable between 1 and 10 reps.

Your inputs are saved in this browser only.

Result

Estimated 1RM (Epley): 262.5 lb
Estimated 1RM (Brzycki): 253.1 lb
Load by reps (%1RM): Reps % 1RM (Epley) Load (Epley) % 1RM (Brzycki) Load (Brzycki)
1 100 % 262.5 lb 100 % 253.1 lb
2 93.8 % 246.1 lb 97.2 % 246.1 lb
3 90.9 % 238.6 lb 94.4 % 239.1 lb
4 88.2 % 231.6 lb 91.7 % 232.0 lb
5 85.7 % 225.0 lb 88.9 % 225.0 lb
6 83.3 % 218.8 lb 86.1 % 218.0 lb
7 81.1 % 212.8 lb 83.3 % 210.9 lb
8 78.9 % 207.2 lb 80.6 % 203.9 lb
9 76.9 % 201.9 lb 77.8 % 196.9 lb
10 75 % 196.9 lb 75 % 189.8 lb; This is a mathematical estimate, not a training recommendation, and does not replace medical advice.

Reps	% 1RM (Epley)	Load (Epley)	% 1RM (Brzycki)	Load (Brzycki)
1	100 %	262.5 lb	100 %	253.1 lb
2	93.8 %	246.1 lb	97.2 %	246.1 lb
3	90.9 %	238.6 lb	94.4 %	239.1 lb
4	88.2 %	231.6 lb	91.7 %	232.0 lb
5	85.7 %	225.0 lb	88.9 %	225.0 lb
6	83.3 %	218.8 lb	86.1 %	218.0 lb
7	81.1 %	212.8 lb	83.3 %	210.9 lb
8	78.9 %	207.2 lb	80.6 %	203.9 lb
9	76.9 %	201.9 lb	77.8 %	196.9 lb
10	75 %	196.9 lb	75 %	189.8 lb

How it is calculated

How the 1RM is estimated

Your 1RM (one-repetition maximum) is the heaviest load you can lift once with good form. Instead of testing it directly, you can extrapolate it from a heavier set taken to failure:

Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)

Example: 225 lb for 5 reps. Epley: 225 × (1 + 5 ÷ 30) = 225 × 1.1667 = 262.5 lb. Brzycki: 225 × 36 ÷ 32 = 253.1 lb. At 10 reps both formulas give the same result; below that Epley estimates slightly higher, above it Brzycki does.

The %1RM chart

The chart inverts each formula and shows roughly which load fits 1 to 10 reps. By Epley, 5 reps correspond to about 85.7% of 1RM, by Brzycki to 88.9%; 10 reps equal 75% in both. For a single rep the calculator uses the weight itself as the 1RM.

Where the formulas come from

The Brzycki formula was published in 1993 in the Journal of Physical Education, Recreation & Dance. The Epley formula goes back to a poundage chart in Boyd Epley's training manual (1985); it is not a peer-reviewed study, but it is widely cited and has been tested in sports science, for example by LeSuer and colleagues (Journal of Strength and Conditioning Research, 1997) for bench press, squat and deadlift.

Limitations

Rep count: the more reps, the less accurate the estimate. Above 10 reps the calculator shows a warning.
Exercise and individual: how many reps you can do at a given %1RM depends on the exercise, training status and muscle fibre type.
Technique: only count clean reps taken to failure.

The result is an estimate, not a training recommendation. It does not replace medical advice, especially if you have health conditions or pain.

Frequently asked questions

What does 1RM mean?

1RM stands for one-repetition maximum: the heaviest weight you can lift once in an exercise with proper technique.

Which is more accurate, Epley or Brzycki?

Neither is better across the board. At low reps they are close, and at exactly 10 reps they are identical. Studies find one or the other closer to the measured value depending on the exercise and group tested.

Why only up to 10 reps?

As reps increase, muscular endurance plays a larger role and the formulas drift further from the true 1RM. Sets of up to about 10 reps give the most reliable estimates.

What percentage of 1RM is 8 reps?

By Epley about 100 ÷ (1 + 8 ÷ 30) = 78.9%, by Brzycki (37 − 8) ÷ 36 = 80.6% of 1RM.

Do I need to test my true 1RM?

No. That is exactly why estimation formulas exist: they avoid a maximal attempt. If you have health concerns, check with a doctor before heavy training.

Sources and legal basis

As of: 27 September 2026