Health
One-repetition maximum (1RM) is the heaviest load you can lift once with proper form. Testing true 1RM is fatiguing and risky for beginners; formulas estimate it from lighter sets.
One-repetition maximum (1RM) is the heaviest load you can lift once with proper form. Testing true 1RM is fatiguing and risky for beginners; formulas estimate it from lighter sets.
Popular equations (Epley, Brzycki, and others) differ slightly by rep range. Estimates degrade above roughly ten reps.
Use 1RM math to program percentages, not to attempt maximal lifts without spotters and preparation. Stop if form breaks down.
Enter the weight you lifted and the number of reps completed (usually 2–10). Calculate to see estimated 1RM and optional training percentages if shown.
This one-rep max (1rm) calculator applies the standard relationship below. Intermediate values are kept at full precision; only the displayed result is rounded.
Epley: 1RM = weight x (1 + reps/30); Brzycki: 1RM = weight x 36 / (37 - reps)
If you lift 100 kg for 5 clean reps, the Epley estimate is 100 × (1 + 5/30) = 116.7 kg. Training percentages follow: 90% ≈ 105 kg, 80% ≈ 93.3 kg, 70% ≈ 81.7 kg.
The calculator applies standard published 1RM estimators configured in the app.
Not automatically—build up with spotters and proper programming.
Estimates are less reliable beyond ~10 reps.
Yes.
The factors and formulas used by this tool follow these references:
Health and fitness results are estimates for general education and planning. They are not medical advice and do not replace an assessment by a doctor, registered dietitian, or other qualified professional.
Last reviewed: September 2026. Found an error? Tell us and we will correct it.
Guides that explain the ideas behind this calculator.
More calculators in Health.