One Rep Max Calculator

Estimate your One Rep Max (1RM) using 6 proven formulas. Get a complete training weight percentage table for strength, hypertrophy, and endurance training.

What is 1RM?

One Rep Max (1RM) is the maximum amount of weight you can lift for one repetition with proper form. It’s a key benchmark for measuring strength and designing effective training programs.

Formulas Used

This calculator uses 6 widely recognized formulas to estimate your 1RM. The average of all formulas is shown as the main result, with individual formula details listed below.

Brzycki: 1RM = W × (36 / (37 - R))
Epley: 1RM = W × (1 + R/30)
Lander: 1RM = (100 × W) / (101.3 - 2.67R)
Lombardi: 1RM = W × R^0.10
O’Conner: 1RM = W × (1 + R/40)
Wathan: 1RM = (100×W) / (48.8 + 53.8×e^(-0.075R))

Frequently Asked Questions

Have another question? Let us know.

Is 1RM testing safe?

Directly testing 1RM carries some risk, especially for beginners. We recommend using this calculator to estimate your 1RM based on multiple-rep weights — it’s both safe and accurate. If you must test directly, always use a spotter.

Why do different formulas give different results?

Each formula was developed based on different research samples and statistical models. The Brzycki formula is most accurate for moderate rep ranges (5-10 reps); Epley performs better at lower rep counts. This calculator averages multiple formulas for improved reliability.

How do I use 1RM percentages in training?

Strength training: 85-100% 1RM, 1-5 reps; Hypertrophy (muscle growth): 67-85% 1RM, 6-12 reps; Endurance training: 50-67% 1RM, 15+ reps. Consider periodizing across different intensity ranges.

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