🏆 One Rep Max Calculator
Testing a true one-rep max is risky and exhausting, so lifters estimate it instead: take a weight you lifted for a few clean reps and the Epley formula projects what you could lift exactly once.
The estimate is most reliable from sets of 1–10 reps done with good form. Coaches then base all training percentages — 70% for volume, 85% for strength — on this number.
How to use this calculator
Enter the weight you lifted and how many clean reps you did, and the tool estimates your one-rep max.
- Enter the Weight lifted in the kg field.
- Enter the Reps completed with good form.
- Read the headline estimated one-rep max.
- Use the 85 percent and 70 percent rows to set training weights.
Frequently asked questions
Which formula does it use?
The Epley formula: one-rep max equals weight times one plus reps divided by 30. Lifting 100 kg for 8 reps estimates a max of about 126.7 kg.
How accurate is the estimate?
Very good for sets of 1 to 10 reps done with strict form. Beyond about 10 reps the projection gets shaky, so test with a moderately heavy set rather than a light high-rep one.
What are the percentage rows for?
Training programs prescribe weights as percentages of your max: around 85 percent builds maximal strength and around 70 percent builds volume and muscle. The rows save you the mental math.
Should I ever test a true max?
Only if your sport needs it, and only with a spotter, safety bars and a full warm-up. For most lifters the estimate is safer and close enough to program from.