One Rep Max (1RM) Calculator

Calculate maximum 1RM lift weight for bench press, squat, and deadlift using Epley and Brzycki formulas.

Overview

Estimates maximum single-repetition lift capacity (1RM) for bench press, squats, and deadlifts using clinically validated Epley and Brzycki strength equations.

Formula & Calculation Method

Epley: 1RM = Weight × (1 + Reps / 30) | Brzycki: 1RM = Weight × [36 / (37 - Reps)]

Predicts maximum lift capacity from submaximal multi-rep sets (1 to 10 repetitions) without requiring dangerous maximal lift attempts.

Worked Example: Lifting 80 kg for 6 Repetitions on Bench Press

Inputs: Weight Lifted = 80 kg | Completed Repetitions = 6 Reps

  • Epley Formula: 80 × (1 + 6 / 30) = 80 × 1.20 = 96.0 kg
  • Brzycki Formula: 80 × [36 / (37 - 6)] = 80 × (36 / 31) = 92.9 kg
  • Averaged Estimated 1RM = ~94.5 kg

Summary: Lift = 80 kg × 6 Reps | Estimated 1RM = 95 kg | 80% Training Weight = 76 kg

Common Use Cases

  • Powerlifting Training Percentages: Calibrate percentage-based strength cycles (e.g. 5/3/1 program sets at 75%, 85%, 95% of 1RM).
  • Benchmark Strength Testing: Test strength gains safely every 8 to 12 weeks without risking joint injury from maximal singles.
  • Workload Periodization: Adjust training loads across hypertrophy (70-80% 1RM) and peak strength (85-95% 1RM) blocks.

Frequently Asked Questions

Why not just test true 1RM directly?

Testing true 1RM carries high injury risk for joints, ligaments, and tendons, and takes days for the central nervous system to recover.

Which 1RM formula is most accurate?

The Brzycki and Epley formulas are both highly accurate for sets between 3 and 8 repetitions; Brzycki tends to be slightly more conservative.

What percentage of 1RM should I lift for muscle hypertrophy?

Hypertrophy training typically utilizes 65% to 80% of 1RM for sets of 8 to 12 repetitions.

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