One-Rep Max Calculator
Estimate your one-rep max from a lifted weight and rep count.
Assumptions used in this calculation
- Formula: Uses the Epley formula (1RM = weight × (1 + reps/30)), one of several common 1RM estimation formulas; results can differ slightly from other methods like Brzycki, especially at higher rep counts.
About this calculator
Testing a true one-rep max at the gym means loading a barbell to a maximal, potentially risky single lift, most lifters would rather not attempt that regularly just to track strength progress or set percentage-based training loads. This calculator estimates your theoretical 1RM instead, using the Epley formula, from a submaximal set: enter the weight you lifted and how many reps you completed, and it calculates 1RM = weight × (1 + reps/30). That single multiplication is simple enough to do by hand, but the calculator saves the step and lets you quickly compare estimates across different rep ranges. The estimate is most reliable for sets of roughly 1-10 reps; very high rep sets (15+) push the formula outside where it was validated and produce less trustworthy numbers. Knowing your estimated 1RM is useful for programming percentage-based training (e.g. "work at 80% of 1RM") without needing to test the actual lift.
Worked example
100 kg for 5 reps
Result: Estimated 1RM ≈ 116.7 kg
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