One Rep Max Calculator — Epley and Brzycki

Your one rep max is the heaviest load you can lift once. You do not have to attempt it to know it: a set taken close to failure carries the same information, and two formulas turn that set into a number. Enter the weight and the reps you completed — the calculator is in kilograms, so 176 lb goes in as 80 kg.

The two formulas doing the work

• Epley: 1RM = weight × (1 + reps ÷ 30)
• Brzycki: 1RM = weight × 36 ÷ (37 − reps)

Run 176 lb (80 kg) for 5 reps through both. Epley returns 93.3 kg (206 lb); Brzycki returns 90.0 kg (198 lb); the average this page shows is 91.7 kg (202 lb). The gap is under 4%, which is typical inside the useful range. The two curves cross at exactly 10 reps and separate on either side — Epley climbs in a straight line forever, Brzycki bends toward a wall at 37 reps, where its denominator runs out. Neither behavior is realistic at high rep counts, which is the first practical reason to keep the test set short.

Why coaches estimate instead of testing

A real max attempt is a protocol, not a set: long warm-up ramp, single reps at rising loads, full recovery between them, and a spotter or safety pins for the lifts where a failed rep pins you under the bar. Most people training for size or general strength get nothing from that ritual that a set of 3 to 8 reps does not already tell them. The estimate is also repeatable week to week without leaving you wrecked for the rest of the session.

How wrong the number can be

Wrong enough to matter. Mayhew’s team compared 14 published prediction equations against measured bench press maxes in 103 college women, before and after 12 weeks of training. After training, the best-performing equations — Brzycki and Lombardi among them — landed within 2.3 kg of the real max for 58% of participants. That is the good case: roughly four lifters in ten were off by more than 5 lb, using the equation that did best on that sample.

Two consequences follow. Use the output as a training reference, not as a number to announce. And recheck it periodically from a fresh set, rather than projecting a percentage program off an estimate that is six months old.

Same math, one lift at a time

The formula does not know which exercise you did — only the weight and the reps. What changes between lifts is the load you start from, the rep range that keeps technique honest, and how you fail safely:

• Bench press max calculator
• Squat max calculator
• Deadlift max calculator
• Overhead press max calculator
• Bicep curl max calculator

To see each equation on its own, open the Epley formula calculator or the Brzycki formula calculator, and compare all three classic models on Epley vs Brzycki. To turn the result into working loads, use the 1RM percentage chart.