One-rep max calculator
Estimate your one-rep max from any set — no maxing out required.
Use good form and count only clean reps. The estimate is most accurate at about 10 reps or fewer. Units are whatever you enter (lb or kg).
Estimated 1RM
How a one-rep max is estimated
Your one-rep max (1RM) is the most weight you can lift for a single rep. Maxing out for real is risky and tiring, so lifters estimate it from a lighter set instead. This calculator uses the Epley formula, one of the most widely used, which stays accurate for sets up to around ten reps.
The formula
Worked example
Lift 100 for 5 clean reps: 1RM = 100 × (1 + 5 ÷ 30) = 100 × 1.167 ≈ 117. From there, 80% (about 93) is a solid weight for sets of eight.
Frequently asked questions
What is a one-rep max?
Your one-rep max, or 1RM, is the heaviest weight you can lift for a single repetition of an exercise. It's a common benchmark for setting training loads.
Do I have to actually max out?
No — that's the point of the estimate. You lift a comfortable, well-formed set of a few reps, and the formula projects your 1RM without the risk of a true max attempt.
How accurate is the estimate?
It's a close approximation for sets of about 10 reps or fewer. Accuracy drops with very high-rep sets, since endurance starts to matter more than raw strength.
How do I use the training percentages?
Strength programs are often written as percentages of your 1RM. The table shows common working loads — for example, around 80% for sets of eight.
Health disclaimer: This calculator is a general estimate, not a medical diagnosis or a substitute for professional advice. See our full disclaimer and talk to a doctor or qualified clinician before acting on the result.