🏋️ One-Rep Max Calculator
Enter a weight and the reps you hit with it to estimate your one-rep max with the Epley and Brzycki formulas, plus a full percentage table for programming your training loads.
🏋️ Estimate Your Max
What is a One-Rep Max Calculator?
Your one-rep max is the most weight you can lift for a single clean repetition, and it is the reference point most strength programs are built around. Testing a true max is risky and tiring, so this calculator estimates it from a lighter set you can complete for several reps, using the well-established Epley and Brzycki formulas.
Use it to set your working weights, track progress over time, and program sets as a percentage of your max. The result is a general fitness estimate, not medical advice — consult a doctor or qualified trainer, warm up thoroughly, and always use proper form, since heavy lifting carries injury risk.
❓ Frequently Asked Questions
How accurate is an estimated one-rep max?
Rep-max formulas like Epley and Brzycki are most accurate in the 1–10 rep range; beyond that, fatigue and technique drift make the estimate looser. They are a planning tool, not a guarantee — use the number to set training loads, then confirm with a properly coached, fully warmed-up attempt if you ever test a true max.
Why do Epley and Brzycki give different numbers?
Each formula was fitted to different lifting data, so they weight reps slightly differently. Epley tends to read a touch higher at higher reps and Brzycki a touch lower. Showing both gives you a sensible range rather than a single false-precision figure.
How do I use the training percentages?
Most strength programs prescribe sets as a percentage of your 1RM — for example 5×5 at 80% or speed work at 60%. The percentage table turns your estimated max into ready-to-load weights so you can program a session without doing the math each time.