One Rep Max Calculator
Estimate your maximum strength for any lift
📊 Enter Your Lift Data
🏆 Your Estimated 1RM
Estimated One Rep Max
📐 Results by Formula
📋 Training Weight Reference
| % of 1RM | Weight | Typical Reps |
|---|
Note
These are estimates based on mathematical formulas. Your actual 1RM may vary based on factors like fatigue, form, and training experience. Always use a spotter when attempting maximal lifts.
About One Rep Max Calculator
Estimates your one-rep max — the heaviest weight you could lift once — from a set you have already completed. Enter the weight and the number of clean reps, and several established formulas are applied.
Why several formulas rather than one
Epley, Brzycki, Lombardi and O'Conner each model the rep-to-weight relationship slightly differently, and they diverge as reps climb. Epley and Brzycki agree closely at 10 reps but drift apart beyond it. Seeing a range rather than a single number is more honest: the true value sits somewhere inside it, and the spread tells you how uncertain the estimate is.
How many reps give the best estimate?
Between 3 and 6. Below 3 there is little to extrapolate from; above about 10 the estimate degrades sharply because endurance rather than strength starts limiting the set. A 20-rep set tells you almost nothing about a single maximal lift.
Safety note
These are estimates from population data, not a prediction for your body on the day. Sleep, nutrition, warm-up and technique all move actual maximum strength substantially. Never load a bar to a calculated max without progressive warm-up sets, a spotter or safety pins, and never let an estimate override how the weight feels. If you are new to lifting or returning from injury, work with a qualified coach rather than a calculator.