Health
One Rep Max Calculator
Enter a weight and the reps you managed with it. The three formulas rarely agree exactly, and the fewer the reps, the more you can trust the answer.
The link carries your figures, so it reopens on exactly these numbers.
The same lift, read at different rep counts
The estimate climbs as the reps rise — but so does the doubt, because the formulas were built to extrapolate from near a true max. Read down the column: the higher the reps, the more the answer is a guess dressed as a number.
| Reps to failure | One-rep max (average of three) | Spread as a share of the average |
|---|---|---|
| 1 repNearly a measurement — but Epley alone reads 103.3, not 100. | 101.1 | 3.3 |
| 3 reps | 109.2 | 5.2 |
| 5 repsThe default above. Average 115.5, about 4.3% apart. | 115.5 | 4.3 |
| 8 reps | 124.6 | 2.8 |
| 10 repsEpley and Brzycki agree here by construction; Lombardi does not, and none is close to a real max. | 130.9 | 5.7 |
The formula
Worked example
100 kg lifted for 5 reps
- Epley: 100 × (1 + 5 ÷ 30) = 116.7
- Brzycki: 100 × 36 ÷ 32 = 112.5
- Lombardi: 100 × 5^0.10 = 117.5
- a spread of 5.0 — about 4.3% between the highest and lowest
Where this goes wrong
Trusting an estimate from a high rep count
All three formulas are only reliable near a true max. At 100 kg for 5 reps they give 112.5, 116.7 and 117.5 — a 5.0 kg spread, about 4.3%, and that is before the ±10% these estimates can sit from an actual one-rep max. The further from a single rep you test, the softer the number: a one-rep max read off a 10-rep set is the least trustworthy of all. There is also a quirk worth knowing — Epley reads high at exactly one rep, returning 103.3 for 100 kg lifted once, when the answer should simply be 100. Pick a set that fails at a low rep count, treat the estimate as a starting point rather than a record, and remember a one-rep max is specific to the exact lift you tested.
Questions
- Which one-rep-max formula is best?
- None is clearly best, and they disagree by about five percent. Brzycki is the most conservative and reads low; Lombardi reads highest at low reps; Epley sits between them but over-reads at a single rep. For a working number, take the range rather than one formula, and test with a low rep count where all three are closest to a real max.
- How accurate is an estimated one-rep max?
- Usually within about ten percent of a true max, and closer when the rep count is low. The estimate is least accurate for beginners, whose strength is changing quickly and whose form is still settling, and for high rep counts far from a single-rep effort. It is a training reference, not a competition result.
- Does the unit matter — kilograms or pounds?
- No. Every one of these formulas multiplies the weight you lifted by a factor that depends only on the reps, so the answer comes out in whatever unit you entered. A hundred kilograms for five reps and a hundred pounds for five reps give the same numbers, each in its own unit.
- Is my one-rep max the same for every exercise?
- No — it is specific to the exact lift. A bench-press max says nothing about a squat or deadlift max, because different exercises recruit different muscles over different ranges. Estimate and track a one-rep max separately for each lift you care about.