One rep max calculator

How do I calculate my one rep max?

Lift a weight you can do for several clean reps, then use a formula. By Epley, 1RM = weight × (1 + reps ÷ 30): 225 lb for 5 reps estimates 262.5 lb.

Which 1RM formula is best?

No single formula fits everyone, so the calculator shows three — Epley, Brzycki and Lombardi — and their average. For 225 lb × 5 they give 262.5, 253.1 and 264.3 lb.

How many reps should I use?

Brzycki wrote that his formula is valid only for fewer than 10 reps, and a 2006 review gives similar limits for Epley and Lombardi. With more reps the formulas drift apart.

How do I find a training weight for a set of reps?

The table turns your estimated max back into weights for 1 to 12 reps with the Epley formula.

Is it safe to test a true one rep max?

A true max attempt puts a lot of load on the body. Estimating from lighter sets avoids it; if you do test, use a spotter and proper warm-up.

What percent of my 1RM is a set of 10?

Solving the Epley formula backward, a set of 10 uses about 75% of your max and a set of 5 about 85.7%. If your estimated max is 234.3 lb, ten reps would be about 175.8 lb.

Why does my estimate differ from what I can actually lift?

All three formulas are fitted curves, not laws. They assume the set was taken close to failure, so a set that stopped with reps still in reserve gives an estimate that is too low. Technique, fatigue, and the exercise itself also move the real number.

Can I use the result for any exercise?

The formulas were built around common barbell lifts and give rough numbers elsewhere. Treat the result as a planning figure, and re-test with a lighter set every few weeks as you get stronger.

The three formulas

With w the weight lifted and r the repetitions completed: Epley gives 1RM = w × (1 + r ÷ 30), Brzycki gives 1RM = w × 36 ÷ (37 − r), and Lombardi gives 1RM = w × r^0.10. Each was fitted to lifters who performed a set to fatigue, so each assumes the last rep was close to your limit. For one rep the answer is simply the weight itself. Brzycki’s denominator reaches zero at 37 reps, one more reason the calculator accepts at most 30.

A worked example

Say you lift 185 lb for 8 clean reps. Epley: 185 × (1 + 8 ÷ 30) = 234.3 lb. Brzycki: 185 × 36 ÷ 29 = 229.7 lb. Lombardi: 185 × 8^0.10 = 227.8 lb. The average is 230.6 lb, and the three estimates sit within 6.6 lb of each other, which is typical in the 5 to 10 rep range.

Why high-rep sets give shaky answers

The formulas agree at low reps and drift apart as reps climb. For 225 lb × 15 the calculator returns 295 lb (Lombardi), 338 lb (Epley) and 368 lb (Brzycki), a spread of about 73 lb. Endurance, rest between reps and the exact exercise matter more as the set gets longer, so use a set of about 3 to 8 reps when you want a number you can trust.

Common mistakes

Counting reps that were not clean (bounced, shortened or assisted) inflates the estimate. Stopping a set well short of failure and entering it as a max-effort set deflates it. And a result is only as consistent as your test conditions: compare numbers from the same exercise, with similar rest and warm-up, rather than across different lifts or days.

Sources: the Epley formula (1985), Brzycki’s formula (M. Brzycki, “Strength testing — predicting a one-rep max from reps-to-fatigue”, Journal of Physical Education, Recreation & Dance, 1993) and Lombardi’s formula (Beginning Weight Training, 1989), as compared in published reviews of 1RM prediction. Related: BMI calculator, calorie calculator, protein calculator and target heart rate calculator.

For general information only — not medical advice. Talk with your doctor or another health professional about your own health. How we check our calculators.