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One-rep max (1RM) calculator
Your one-rep max (1RM) is the heaviest weight you could lift once in an exercise. Testing it for real is demanding and risky, so it's usually estimated from a set of several reps.
We use the Epley formula, one of the most widely used, which works best with sets of 1 to 10 reps. From your estimated 1RM we work out the loads for training at 90, 80 and 70%.
Frequently asked questions
Is it safe to test my real 1RM?
Only with experience, good form, a warm-up and a spotter. For most people, the estimate is enough and safer.
Why is my 1RM useful?
It helps you pick the right load for your goal: around 80–90% for strength and 65–80% for muscle growth.
Why is it less accurate with high reps?
Above 10 reps individual endurance plays a big role and the formula loses precision.
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