One Rep Max Calculator

The one-rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise. Knowing your 1RM is the foundation of intelligent strength programming because most quality training percentages — 60% for speed work, 80% for hypertrophy, 90%+ for max strength — are expressed relative to it.

Testing a true 1RM is risky and fatiguing, so coaches use submaximal estimation formulas. The Epley formula (weight × (1 + reps/30)) and Brzycki formula (weight × 36/(37 − reps)) are two of the most widely used and agree closely for sets between 2 and 10 reps. Beyond 10 reps, accuracy degrades because endurance, not strength, becomes the limiting factor.

Use the training percentages table to plan your next mesocycle. For example, if your estimated bench 1RM is 250 lbs, working sets of 5 at 200 lbs (80%) build strength while leaving you fresh enough to train hard the rest of the week.

One-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. Knowing your 1RM lets you prescribe training loads as a percentage — 5×5 at 80% for strength, 3×8 at 70% for hypertrophy, 5×3 at 90% for peaking. Most lifters never actually test a true 1RM because the risk-reward is poor; using calculator-estimated 1RMs from sets of 3–10 reps is the standard approach in modern programming.

Epley and Brzycki are the two most popular formulas, and they agree closely up to about 10 reps. Above 10 reps, accuracy drops sharply because muscular endurance, not strength, becomes the limiting factor. For sets above 10 reps, treat the 1RM estimate as a rough guideline only. The most accurate predictions come from sets in the 3–6 rep range, which is also where most strength-focused programs do their working sets.

Bar speed is now the gold standard for autoregulating training. Velocity-based training tools like Tendo Units and Vitruve track bar speed in m/s; a drop below a target velocity signals that the working weight has become too heavy for that day. Lifters without expensive equipment can self-rate using RPE (rate of perceived exertion) on a 1–10 scale, where 10 is a true maximum and 8 leaves two reps in the tank.

1RMs are not static. They fluctuate day-to-day with sleep, nutrition, stress and training fatigue. A 5% swing in any direction is normal even for an advanced lifter. This is why good programs prescribe ranges (75–82%) rather than exact percentages, and why testing should happen at the end of a deload, not at the end of a hard training block. Use this calculator as a planning anchor, not as a precise daily prescription.