1RM Calculator
Enter the weight you lifted and the number of reps completed to estimate your one-rep max (1RM) using both the Epley and Brzycki formulas. The calculator also generates a training percentage table showing recommended weights for different intensity zones (65%–100% of 1RM).
1RM Calculator
Estimate your one-rep max using the Epley and Brzycki formulas. Enter a weight and rep count from a recent set.
Frequently Asked Questions
Your one-rep max is the maximum weight you can lift for a single repetition with proper form. It's used in strength training to program workout intensity — for example, training at 80% of your 1RM for hypertrophy or 90%+ for maximal strength.
The Epley formula (1RM = weight × (1 + reps/30)) tends to give slightly higher estimates at higher rep ranges. The Brzycki formula (1RM = weight × 36 / (37 − reps)) is considered more accurate for sets under 10 reps. Both diverge more significantly above 10 reps.
Estimation formulas are most accurate for sets of 1–6 reps and become less reliable above 10 reps. They typically have an error margin of ±5% for low rep ranges. For the most accurate result, use a weight you can lift for 3–5 reps with good form.
Direct 1RM testing is stressful on the body and should be done infrequently — typically every 8–12 weeks at the end of a training cycle. Estimation from sub-maximal sets (like this calculator provides) is a safer way to track strength progress more frequently.