Health & Fitness Calculators
One Rep Max Calculator
Estimate your one-rep max from a lift.
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About the One Rep Max Calculator
Your one-rep max (1RM) is the most weight you can lift for a single rep — the benchmark for programming strength training. Enter a weight and the reps you completed and the calculator estimates your 1RM using the Epley formula, plus the loads for common rep ranges (95%, 80%, 70%). It's the safe way to find your max without actually attempting a risky single.
How to use the One Rep Max Calculator
- 01Enter your weight lifted and reps performed.
- 02Read the result instantly — it recalculates as you type.
- 03Adjust the numbers to model different scenarios.
Frequently asked questions
How is one-rep max estimated?
The Epley formula: 1RM = weight × (1 + reps ÷ 30). It's most accurate for sets under about 10 reps.
Why use a percentage chart?
Strength programs prescribe loads as a percentage of 1RM. The chart converts your max into working weights for different rep ranges.