One Rep Max Calculator
Estimated 1RM plus a full percentage table.
Entered in kilograms.
Estimates assume the set was taken close to failure. Above about 10 reps the result reflects muscular endurance more than strength, and accuracy drops sharply.
Estimated one rep max
115.5 kg
from 5 reps at 100 kg
Training guide: 85-95% for strength, 70-85% for hypertrophy, under 70% for endurance and technique.
How the One Rep Max Calculator works
A one rep max is the heaviest single repetition you can complete with good form. Testing it directly is fatiguing and carries some risk, so most lifters estimate it from a set of moderate reps — accurate up to about eight reps, and increasingly optimistic beyond that.
Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.
Frequently asked questions
How accurate are 1RM estimates?
Within about 5% when the set was genuinely near failure at 8 reps or fewer. Accuracy falls off sharply past 10 reps, where the result depends more on muscular endurance than on strength. The set has to be close to failure — reps left in reserve inflate nothing, they just deflate the estimate.
Which 1RM formula is best?
Epley and Brzycki agree closely at low rep counts and diverge above 10. Brzycki tends to read lower at high reps, Epley higher. Since neither is definitive, using the average of several is a sensible default.
How should I use percentage of 1RM?
Broadly: 85-95% for strength in the 1-5 rep range, 70-85% for hypertrophy at 6-12 reps, and under 70% for endurance and technique work. Your true daily maximum fluctuates with sleep, stress and nutrition, so treat percentages as guides rather than prescriptions.
Is it safe to test a true 1RM?
For an experienced lifter with sound technique, a spotter and a proper warm-up, yes. For beginners it is generally unnecessary — technique is still changing week to week, and an estimate from a 5RM gives you everything you need to program.