One-Rep Max (1RM) Calculator
Estimate your one-rep max from a submaximal set using the Epley and Brzycki formulas, then read your working weights straight off the percentage table.
Estimated one-rep max
Training loads from your max
| % of 1RM | Weight | Approx. reps |
|---|---|---|
| 95% | 108.9 kg | 3 |
| 90% | 103.1 kg | 4 |
| 85% | 97.4 kg | 6 |
| 80% | 91.7 kg | 9 |
| 75% | 85.9 kg | 11 |
| 70% | 80.2 kg | 14 |
| 65% | 74.5 kg | 17 |
| 60% | 68.8 kg | 21 |
The Epley and Brzycki formulas agree closely at low reps and drift apart as reps climb, so the average is the most robust single figure. This is an estimate, not a tested max — warm up and use safeties before attempting a true one-rep max.
Why your 1RM is worth knowing
Almost every strength program is written in percentages of a one-rep max: work up to a heavy triple at 90%, hit your back-off sets at 70%, deload at 60%. But testing a true max is fatiguing and risky, so most lifters estimate it instead. Feed in a set you actually did — the weight and how many clean reps you managed — and the Epley and Brzycki formulas project the single-rep load behind it.
With that number in hand, the percentage table turns your whole program into concrete weights you can load on the bar, and re-estimating every few weeks from your best working sets is a low-risk way to watch your strength climb.
Frequently Asked Questions
How is a one-rep max estimated without testing it?
You lift a submaximal weight for a known number of reps, and a formula projects the single-rep load from that. This calculator runs two of the most established formulas — Epley (1RM = weight × (1 + reps/30)) and Brzycki (1RM = weight × 36 / (37 − reps)) — and averages them. Because you never actually attempt a maximal single, it's far safer than a true one-rep-max test while still giving a usable number.
Why do Epley and Brzycki give different numbers?
They fit slightly different curves to the reps-versus-load relationship. At a single rep they both return the weight itself, and around eight to ten reps they land very close together. In between and beyond, Epley tends to read a little higher than Brzycki. Averaging the two smooths out the disagreement, which is why we show the average as the headline figure.
How many reps should I use for the most accurate estimate?
Fewer reps means less extrapolation and a more reliable estimate. A set of two to five reps taken close to failure gives the best read. The further past ten reps you go, the more the formulas drift, so this tool caps input at twelve reps.
Should I actually attempt the estimated max?
Treat the number as a training reference, not a target to test cold. If you do want to work up to a heavy single, do it with a full warm-up, good technique, a spotter or safeties, and gradual jumps. An estimate is a planning tool, not a guarantee of what will move on the day.
Educational estimate only — not medical, fitness, or training advice. Estimated maxes and percentages vary by lifter, lift, and day. Warm up thoroughly, use proper form and safeties, and consult a qualified coach or physician before attempting heavy loads or starting a new program.