One Rep Max Calculator — Test Your 1RM Without Risking It

How to use

1. Enter weight & reps — your best hard set (most accurate at 1–8 reps).
2. Compare formulas — Epley and Brzycki estimates shown side by side.
3. Use the % chart — pick training weights by goal: strength, hypertrophy or endurance.

General information only — not medical, financial or legal advice. Figures cross-checked against public official sources (IRS / HMRC / NHS / WHO guidance); content last reviewed September 2026. For decisions that matter, confirm with a licensed professional in your country.

About this tool

Actual 1RM attempts are the riskiest lifts in the gym. The smarter way: take a hard set of 1–10 reps and estimate the max with the two validated formulas — Epley (w × (1 + reps/30)) and Brzycki (w × 36/(37 − reps)), which agree closely under 10 reps. You also get the percentage chart powerlifters program with: 90% for heavy singles, 80% for strength, 70% for hypertrophy volume, 60% for speed work — so the estimate turns directly into a training plan.

From RPE to 1RM: Read Your Set Right (2026 Guide)

The calculator runs two validated formulas — Epley w × (1 + reps/30) and Brzycki w × 36/(37 − reps) — on any hard set, then builds a percentage table for training targets. The rep you feed it is where RPE comes in: read your set honestly and the estimate lands within a few pounds of your true max. Here is the mapping, a worked example, and where each formula bends.

RPE → what to enter

RPE 10 means the bar stopped moving — the rep you just grinded was your last. Each point below 10 is one rep left in the tank. The calculator wants total reps you could have completed at that weight, so:

Worked example: 225 lb × 5 at failure

Epley: 225 × (1 + 5/30) = 262.5 lb. Brzycki: 225 × 36/(37 − 5) = 253.1 lb. The tool shows both plus a usable average; from there it builds the training table — on a ~258 lb working estimate: 95% ≈ 245 (heavy singles), 90% ≈ 232 (doubles), 85% ≈ 219 (strength), 80% ≈ 206 (strength/hypertrophy), 75% ≈ 194 (power), 70% ≈ 181 (8–12 rep hypertrophy), 60% ≈ 155 (speed/endurance). Enter the same set at RPE 8 instead — that is 7 total reps — and Epley rises to 277.5, which is exactly why RPE honesty is the whole game: two reps of overconfidence inflates your programmed training max by nearly 6%.

Under five reps the two formulas agree within ~4%; above ten, Epley drifts high and Brzycki punishes endurance sets, so treat those numbers as ceilings. Estimated maxes also run conservative against a true peaked 1RM — adrenaline, grip, and technique add pounds math cannot see. Program off the estimate, retest the estimate every few months, and let the BMI calculator and body fat calculator track the composition side of the same training block.

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