One Rep Max Calculator
Estimate your one-rep max (1RM) from the weight and reps of a working set.
Estimated 1RM116.7kg
95% of 1RM110.8kg
80% of 1RM93.3kg
This uses the Epley formula: 1RM = weight × (1 + reps ÷ 30). Lifting 100 kg for 5 reps estimates a one-rep max of 100 × (1 + 5/30) ≈ 116.7 kg. The percentages help you pick training loads. Estimates are least accurate above about 10 reps.
Educational estimate only — not professional financial or medical advice.
Questions
How is one-rep max estimated?
The Epley formula multiplies the weight lifted by (1 + reps ÷ 30). Lifting 100 kg for 5 reps estimates a 1RM of about 116.7 kg.
How accurate is it?
It is a good estimate for sets under about 10 reps. Beyond that, fatigue and technique make the prediction less reliable — never test a true max without a spotter.