How to estimate your one-rep max
You can estimate your one-rep max (1RM) from a set you actually performed, using the weight and the number of reps. Three classic formulas — Epley, Brzycki and Lombardi — do this, and the spread between them is the honest error band. Here they are side by side, with a worked example.
Open the One-Rep Max calculatorThe One-Rep Max Calculator runs all three formulas below on the weight and reps you enter, so you can see the estimate and the spread at once.
Why estimate a 1RM at all?
Testing a true one-rep max is fatiguing and, done often or without a spotter, risky. Estimating it from a submaximal set — say a heavy set of five — lets you program percentages, track progress, and set openers without repeatedly grinding out singles. The estimate is only ever an approximation, but a good one for low-rep sets taken close to failure.
The three formulas
Each takes the weight lifted (w) and the number of reps completed (reps).
They agree closely at low reps and diverge as reps climb.
Epley grows linearly with reps; Brzycki uses a hyperbolic denominator that climbs steeply as reps approach the high 30s (and breaks down entirely at 37 reps); Lombardi applies a gentle power curve. Their different shapes are why they part ways on higher-rep sets.
Worked example: 100 kg for 5 reps
- Epley:
100 × (1 + 5/30) = 100 × 1.16667 = 116.7 kg. - Brzycki:
100 × 36 / (37 − 5) = 100 × 36 / 32 = 112.5 kg. - Lombardi:
100 × 5^0.10 = 100 × 1.17462 = 117.5 kg.
The three land at 112.5, 116.7 and 117.5 kg. That roughly 5 kg range is the error band: your true 1RM is very likely inside it, but no single formula can tell you exactly where. A sensible read here is "about 113–118 kg", not a false-precision "116.7 kg".
Reps to percentage of 1RM (typical range)
A related shortcut is the reps-to-percentage table. Treat it as a typical range, not a rule — the exact percentages differ by person and exercise.
| Reps to failure | Typical % of 1RM |
|---|---|
| 1 | 100% |
| 2 | ~95% |
| 3 | ~93% |
| 4 | ~90% |
| 5 | ~87% |
| 6 | ~85% |
| 8 | ~80% |
| 10 | ~75% |
| 12 | ~70% |
Which formula should you trust?
For sets of about 1–5 reps the three barely disagree, so any of them is fine; take the average or the middle value. For higher-rep sets, the spread widens and the estimate becomes less reliable, so lean on lower-rep testing when you need accuracy. The most useful habit is to pick one formula and stay with it for tracking, while using the spread as a reminder of how uncertain the number is.
What a 1RM estimate does not tell you
All three formulas were fitted mostly to low-rep data, so they diverge sharply above roughly 10 reps and can be well off for high-rep sets. They also differ by exercise — a leg-press estimate behaves differently from a bench estimate — and every formula assumes the set was taken near failure with consistent technique. A set left with reps in reserve, or with breakdown in form, will skew the estimate. Use the number as guidance, and only attempt a true max lift with proper warm-up and a spotter.
Frequently asked questions
Which 1RM formula is most accurate?
None is universally best. For low-rep sets (about 1–5 reps) Epley, Brzycki and Lombardi agree closely, so the average is a good estimate. Accuracy drops as reps rise, so the spread between them is your error band.
How many reps should I use for the best estimate?
Aim for a set of about 3–5 reps taken close to failure. That keeps you inside the range the formulas were fitted for while avoiding the risk of a true single.
Does the estimate work for every exercise?
Roughly, but not identically. The formulas were derived largely from barbell lifts, and the reps-to-percentage relationship varies by movement, so treat cross-exercise numbers as looser.
Related tools and reading
One-Rep Max Calculator
Enter weight and reps to see Epley, Brzycki and Lombardi estimates with the spread.
ReadHow is a Wilks score calculated?
Turn a competition total into a size-adjusted Wilks score with the exact formula.
Sources
- B. Epley (1985), "Poundage Chart," the Epley 1RM estimation equation. Checked 23 Aug 2026.
- M. Brzycki (1993), "Strength testing — predicting a one-rep max from reps to fatigue," the Brzycki equation. Checked 23 Aug 2026.
- V. Lombardi (1989), Beginning Weight Training, the Lombardi power-curve equation. Checked 23 Aug 2026.