One Rep Max Calculator
Calculate your maximum one-repetition lift using multiple scientific formulas.
How One Rep Max Is Calculated
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition. Since testing true 1RM directly can be dangerous, these formulas use submaximal lifts (weight and reps) to estimate your 1RM.
Epley Formula
1RM = Weight x (1 + Reps/30). Most commonly used for bench press and squat.
Brzycki Formula
1RM = Weight x 36 / (37 - Reps). Works well for reps under 10.
Lombardi Formula
1RM = Weight x Reps ^ 0.10. Based on a power curve.
O'Conner Formula
1RM = Weight x (1 + Reps/40). Similar to Epley with a divisor of 40.
About this Calculator
The One Rep Max Calculator is a free, easy-to-use tool for strength, lift, 1RM. Simply enter your values and get instant, accurate results — no signup, no ads, no tracking. All calculations run locally in your browser, so your data stays completely private.
Privacy Note: All calculations are performed locally in your browser. No data is ever sent to a server or third party.