One Rep Max Calculator (1RM)
Estimate your one-rep max and training loads from a set you've lifted.
Result
Estimated 1RM
93.3
Load for ~5 reps
81.2
Load for ~8 reps
74.7
Load for ~10 reps
70.0
How it works
Your one-rep max (1RM) is the most weight you can lift for a single repetition of an exercise. Rather than risk a true max attempt, this calculator estimates it from a weight you lifted for several reps, using a proven formula. The common Epley formula is 1RM = weight × (1 + reps ÷ 30). Lift 100 kg for 5 reps and your estimated max is about 117 kg. Accuracy is best in the low-rep range (up to about 10); beyond that, estimates drift because endurance starts to matter more than raw strength. Lifters use the 1RM to program training: a set at 80% of 1RM, for example, is a typical working weight for building strength. Re-test every few weeks as you get stronger.
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Frequently asked questions
Which 1RM formula does this use?
It uses the widely trusted Epley formula, 1RM = weight × (1 + reps ÷ 30), a reliable estimate for low-to-moderate rep sets.
How accurate is an estimated 1RM?
It is most accurate for sets of about 10 reps or fewer. The more reps you do, the more endurance influences the number and the rougher the estimate.
How do I use 1RM for training?
Take a percentage of it to set working weights — for example, strength work often uses 80–90% of 1RM, while lighter volume work uses 60–70%.
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