One Rep Max Calculator
Estimate your 1RM and training loads
Estimate your one-rep max from a set you've done, then see suggested training weights at 70%, 80% and 90%.
How it works
We use the Epley formula: 1RM = weight × (1 + reps/30). It's most accurate for sets under about 10 reps. Use the percentage loads to program your training without maxing out.
Lift safely — use a spotter and proper form when testing heavy.
Why estimate instead of testing
A true one-rep max attempt is risky and fatiguing, especially without a spotter or much experience. Estimating from a solid set of 3–8 reps gives a number nearly as useful for programming, with far less injury risk. Use a weight you can lift with clean form to failure or one rep shy of it.
Programming with percentages
Most strength programs prescribe work as a percentage of 1RM: roughly 70% for higher-rep hypertrophy sets, 80–85% for strength, and 90%+ for low-rep peaking. The loads shown give you a starting point — round to the nearest plate, and re-test your estimate every few weeks as you get stronger.
One Rep Max Calculator: frequently asked questions
How accurate is an estimated 1RM?
Quite accurate for sets of 2–10 reps; accuracy drops on very high-rep sets.
Should I actually test my 1RM?
Estimating from a submaximal set is safer for most lifters than a true one-rep attempt.
How many reps should I use to estimate my 1RM?
Sets of about 3–8 reps give the most accurate estimate. Very high-rep sets (15+) overstate your max because endurance, not pure strength, becomes the limiting factor. Use clean form and stop a rep shy of failure.