Free tool
One-Rep-Max Calculator
Estimate your 1RM from a set you already lifted, with no max attempt needed, then read your working weight for any percentage.
Epley: – · Brzycki: – · the headline is their average. Most accurate at ~10 reps or fewer.
| Reps | % of 1RM | Working weight |
|---|
Your real max moves every week
Coachero tracks the best-ever effort on every lift as you log, detects PRs automatically, and scores your strength against your bodyweight, so your training percentages follow your actual progress, not a number from one good day.
Track your lifts in CoacheroWhat is a one-rep max?
Your one-rep max (1RM) is the heaviest weight you can lift for a single clean repetition of a given exercise. It's the standard yardstick of maximal strength, and the reference nearly every strength program is written against: "work up to 5×3 at 85%" only means something once you know your max.
Estimate it without maxing out
Testing a true 1RM is fatiguing and, loaded heavy and solo, risky. Instead you can estimate it from a normal set. This calculator averages two well-established formulas:
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Both are most accurate for sets of about ten reps or fewer: the further you get from a true single, the more they drift, so a heavy triple or five predicts better than a set of fifteen.
Training with percentages
Once you have an estimated max, the table turns it into a working weight for each rep count and percentage. Use it to load a program honestly: if the plan says 3×5 at 80%, the table gives the bar weight. Re-estimate every few weeks from your best recent set; a max from two months ago underloads today's session.
1RM questions
How accurate is an estimated 1RM?
Within a few percent for sets under about ten reps, which is close enough to program with. It's an estimate, not a tested max; the fewer reps in the set you enter, the closer it lands.
Which formula is best, Epley or Brzycki?
They agree closely at low reps and diverge slightly as reps climb. Averaging them smooths that out, which is why the headline number here is the mean of the two.
Should I actually test my 1RM?
Occasionally, with a spotter and a proper warm-up, if your sport requires it. For most training, an estimate from your working sets is safer and updates itself every session.
Estimates for general training use, not medical advice. Lift heavy singles only with proper warm-up and a spotter.