One Rep Max (1RM) Calculator
Estimate the heaviest weight you can lift once based on a sub-maximal set.
Formula
Epley: weight × (1 + reps/30)
How to use
- 1Enter the weight you lifted.
- 2Enter the reps you completed with good form (ideally 2 to 10).
- 3Read your estimated 1RM and the 80% and 95% training loads.
About this calculator
Your one rep max is the heaviest weight you can lift once with good form, and it defines strength programs. Testing a true max is risky and often unnecessary, so this calculator estimates it from a set you already did using the Epley formula, then gives you the training percentages to plan your next block.
Formula explained
Epley formula: 1RM = Weight × (1 + Reps ÷ 30). The more reps you manage at a weight, the further it sits below your max, so the formula scales the weight up. It is most accurate for about 2 to 10 reps.
Worked example
80 × (1 + 5 ÷ 30) = 80 × 1.167 = 93.3 kg. An 80% hypertrophy load is about 74.6 kg; a 95% strength load is about 88.6 kg.
Tips & notes
- Only count reps with full range and strict form - sloppy reps inflate the estimate.
- Test when fresh, not at the end of a workout.
- Recalculate every 6 to 8 weeks to track progress and update loads.