One Rep Max Calculator
Turn any completed set into an estimated one rep max using seven established formulas, then read your full training percentage table.
Your best set
Training percentages
| % of 1RM | Weight | Typical reps |
|---|
Formula comparison
| Formula | Estimated 1RM |
|---|
The estimation formulas
Brzycki: 1RM = w × 36 ÷ (37 − r)
Lombardi: 1RM = w × r^0.10
Lander: 1RM = 100w ÷ (101.3 − 2.67123r)
O'Conner: 1RM = w × (1 + 0.025r)
Wathan: 1RM = 100w ÷ (48.8 + 53.8·e^(−0.075r))
Mayhew: 1RM = 100w ÷ (52.2 + 41.9·e^(−0.055r))
w = weight lifted, r = repetitions completed to failure
A one rep max estimate turns a set you actually finished into the single heaviest load you could theoretically move once. All the formulas agree closely at low reps and drift apart as reps climb, which is why a set of three to five is the sweet spot for estimation. Above about ten reps the numbers become guesses shaped by endurance rather than strength.
Train from the percentages, not the max
The value of a 1RM estimate is the percentage table it unlocks. Most hypertrophy work sits between 65 and 80 percent for six to twelve reps, while pure strength work lives above 85 percent for one to five reps. Re-test with a heavy set of three every four to six weeks rather than attempting genuine maximum singles often — the risk to form and joints is rarely worth it.
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