ReadyLiftThis 1RM calculator estimates your one-rep max from a set you have done: enter the weight, the reps, and how many reps you had left in reserve. It uses the Epley and Brzycki formulas, the same ones ReadyLift uses for PRs and program targets, and builds a percentage chart from the result.
Enter a set you did
Most accurate for sets of 1 to 10 reps. Reps in reserve are the reps you could still have done, so a set of 5 with 2 left counts like 7 to failure.
How is a one-rep max estimated?
A one-rep max (1RM) is the most you can lift for a single rep. Formulas estimate it from a heavier set of a few reps, so you never need to test a true max. The Epley formula is weight × (1 + reps ÷ 30); the Brzycki formula is weight × 36 ÷ (37 − reps). This calculator shows both and uses their average.
Reps in reserve (RIR) make the estimate fairer. A set of 5 with 2 reps left is treated like a set of 7 to failure, so an easy set doesn't undersell your strength. Estimates are most reliable from sets of 10 reps or fewer.
How do you use your 1RM in a program?
Percentage-based programs build every set from your max. 5/3/1 and nSuns both use a training max of 90% of your 1RM. Madcow 5x5 uses your 5-rep max instead, which the rep max table above estimates for you.
For how these programs work, see our guides to 5/3/1 Boring But Big and nSuns 5/3/1 LP.
Frequently asked questions
How accurate is a 1RM calculator?
It is an estimate. Formulas are most accurate from sets of 1 to 10 reps and get less reliable at higher reps. Your true max also depends on technique and the day. Use the estimate to set training weights, not as a promise of what you can lift.
Should I test my real one-rep max?
Most programs don’t need it. A training max of 90% of an estimated 1RM leaves enough room for good reps. If you do test a true max, warm up thoroughly and use a spotter or safety bars.
Which formula is best?
Epley and Brzycki give very similar results for sets of up to about 10 reps. Epley reads slightly higher at moderate reps. Averaging them, as this calculator does, keeps you away from either extreme.
What are reps in reserve?
Reps in reserve (RIR) are the reps you could still have done when you stopped the set. RIR 0 means you went to failure; RIR 2 means two more were possible. ReadyLift logs RIR with every set.
General training information, not medical advice. If you have an injury, a heart condition or another health concern, check with a doctor or physical therapist before starting a new program.