Free lifting tool
One Rep Max Calculator
Estimate your one-rep max from any set of 1–12 reps, then see the weights to use for every rep range.
Estimated 1RM
114.6 kg
Composite average of Brzycki (112.5 kg) and Epley (116.7 kg) formulas
Repetition Maximum Breakdown
How the 1RM calculator works
Your estimated one-rep max (e1RM) is the heaviest weight you could probably lift once, worked out from a heavier set of several reps. This calculator averages two widely used formulas:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Estimates are most accurate at 10 reps or fewer, from a set taken close to failure. Past about 12 reps the formulas drift, because endurance matters more than maximal strength.
Using your 1RM to plan training
Most strength programs set working weights as a percentage of 1RM: roughly 85–90% for sets of 3–5 and 70–75% for sets of 10–12. Pick a program from the free programs library and use the table above to choose your starting weights.
Frequently asked questions
How accurate is a one-rep max calculator?
For sets of 2–10 reps taken close to failure, estimates are usually within about 5% of a true 1RM. Accuracy drops for high-rep sets and for lifters who are much stronger or weaker at high reps than average.
Which 1RM formula is best?
Epley and Brzycki give almost identical results around 5 reps. Brzycki tends to read lower at higher reps. This calculator averages the two.
Should I test my real 1RM?
You don’t need to. Most lifters get stronger just as well working from an estimated 1RM, and it skips the fatigue and injury risk of maximal attempts.
Stop doing gym maths in your head.
RepEight calculates your 1RMs, plates and PRs automatically as you log.
Scan to download