Which 1RM formula is most accurate?

Epley and Brzycki are the most common and give very similar results at low reps. All formulas lose accuracy above about 10–12 reps, where endurance rather than strength limits the set.

Why use one-rep max percentages?

Strength programs prescribe loads as a percentage of 1RM — for example 5 reps at 80%. Estimating your 1RM lets you set training weights without repeatedly testing a true max, which is fatiguing and riskier.

One Rep Max Calculator

Q: How do I calculate my one-rep max?

Estimate it from a lighter set. The Epley formula is 1RM = weight × (1 + reps ÷ 30). Lifting 225 lb for 5 reps estimates a 1RM of about 262 lb. Accuracy is best at 10 reps or fewer.

Estimate your one-rep max from a set you've actually done — then use the percentage table to program your training loads.

Estimated one-rep max

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% of 1RM	Weight	Typical reps

The formulas

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

Worked example

225 lb × 5 reps → Epley: 225 × (1 + 5/30) = 262 lb. Brzycki gives ≈ 253 lb — close agreement at low reps.

Training with percentages

% 1RM	Reps	Focus
100%	1	Max strength
90%	3–4	Strength
80%	6–8	Strength + size
70%	10–12	Hypertrophy
60%	15+	Endurance

Estimating your max from a submaximal set is safer than testing a true one-rep max, especially for beginners. Keep the test set at 10 reps or fewer for accuracy — beyond that, endurance clouds the strength estimate. Use the percentages to auto-set working weights (e.g. "5×5 at 80%"), and re-estimate every few weeks as you get stronger. Track your training energy needs with the calories burned and protein calculators.

Frequently asked questions

How do I calculate my one-rep max?

Epley: weight × (1 + reps/30). 225×5 ≈ 262 lb. Best at ≤10 reps.

Which formula is most accurate?

Epley and Brzycki agree closely at low reps; all lose accuracy above ~10–12 reps.

Why use 1RM percentages?

Programs prescribe loads as % of 1RM, so estimating it sets training weights without maxing out.

Related calculators

Medical disclaimer: An estimate for training, not medical advice. Lift with proper form and a spotter for heavy attempts; consult a professional if you have injuries or health conditions. Formulas: Epley & Brzycki. Last reviewed: July 2026.