Overview
Your one-rep max (1RM) is the heaviest weight you can lift for a single rep. It's the reference point for programming intensity, but testing it directly is risky and fatiguing. This calculator estimates it from a set you've already done.
How it's calculated
Enter the weight you lifted and the reps you completed, then pick a formula. Epley tends to read slightly higher at high reps; Brzycki is conservative and best under ~10 reps. The percentage table shows training loads derived from your estimate.
Epley: 1RM = weight × (1 + reps / 30) Brzycki: 1RM = weight × 36 / (37 − reps)
How to read your result
Use the estimate to set working weights — e.g. hypertrophy work often sits at 67–80% (8–12 reps), strength work at 85%+ (1–5 reps). Estimates get less accurate above ~10 reps, so base 1RM off sets of 5 or fewer when you can.
Frequently asked questions
Which formula is most accurate?
For low reps (≤5) Epley and Brzycki are very close. Brzycki is more conservative as reps climb; Epley slightly higher. Use the same formula consistently to track progress.
How many reps should I use?
Sets of 3–5 reps give the most reliable estimate. Above 10 reps, accuracy drops because endurance starts to dominate.
Is it safe to skip maxing out?
Yes — estimating from a submaximal set avoids the injury and fatigue risk of a true 1RM attempt, which is why most programs use estimated maxes.
Sources & references
- Brzycki M. Strength testing—predicting a one-rep max from reps-to-fatigue. JOPERD. 1993;64(1):88-90.
- Epley B. Poundage chart. Boyd Epley Workout. Lincoln, NE; 1985.