One-Rep Max Calculator
Estimate your one-rep max (1RM) from a weight you lifted for multiple reps, using the Epley, Brzycki and Lombardi formulas side by side. The spread between them is your honest error band.
Formulas: Epley (1985), Brzycki (1993), Lombardi (1989) • Checked 24 Aug 2026Enter your set
Why this tool shows three numbers, not one
A one-rep max (1RM) is the most weight you can lift for a single repetition. Testing it directly is fatiguing and, done carelessly, risky, so it is usually estimated from a submaximal set taken close to failure. The catch: there is no single agreed equation. Three have been in print for decades, and they disagree. Rather than hide that behind one confident figure, this calculator runs all three and shows the gap between them — the honest error band on your estimate.
- w
- the weight lifted for the set
- reps
- repetitions completed, close to failure
All three agree exactly at one rep and drift apart as reps climb. Read the spread, not just the average: a tight spread means the estimate is trustworthy; a wide one means treat the number with caution.
Reading the spread: 100 kg for 5 reps
- Epley:
100 × (1 + 5/30) = 116.7 kg - Brzycki:
100 × 36 / (37 − 5) = 112.5 kg - Lombardi:
100 × 5^0.10 = 117.5 kg
The estimates run 112.5–117.5 kg — a 5 kg band around an average of about 115.6 kg. At 5 reps that band is narrow, so ~116 kg is a fair working figure. Repeat the same set at 12 reps and the band widens past 15 kg, which is the calculator's way of telling you the high-rep estimate is a guess, not a number to load a bar with.
Turn your 1RM into training weights
An estimate is only useful once it sets the weight on the bar. Programs are written as percentages of 1RM, so here is a ~116 kg 1RM (the example above) mapped to the loads and rep counts each training goal calls for. Scale the percentages to your own 1RM:
| % of 1RM | Load (116 kg 1RM) | Typical reps | Training focus |
|---|---|---|---|
| 90–95% | 104–110 kg | 2–4 | Maximal strength |
| 85% | ~98 kg | 5–6 | Strength |
| 80% | ~93 kg | ~8 | Strength / hypertrophy |
| 70–75% | 81–87 kg | 10–12 | Hypertrophy |
| 60–67% | 70–78 kg | 15+ | Muscular endurance |
These percentage bands are the widely used strength-training continuum; the exact reps you hit at each load still depend on the exercise and how fresh you are. When your working sets start feeling light, re-estimate — for most lifters that is every 4–8 weeks, or at the end of a training block. Testing more often just adds fatigue before your program has had time to move the number.
Reps-to-percentage quick reference
The reverse lookup: if you know a set's rep count, roughly what percentage of 1RM were you lifting? Handy for sanity-checking an estimate or reverse-engineering a 1RM from a logged working set. Derived from the Epley relationship, it is a typical range, not a rule — the true percentage shifts with the exercise, your training history and how close to failure you went.
| Reps | Approx. % of 1RM |
|---|---|
| 1 | 100% |
| 2 | ~95% |
| 3 | ~90% |
| 4 | ~88% |
| 5 | ~86% |
| 6 | ~83% |
| 8 | ~79% |
| 10 | ~75% |
| 12 | ~71% |
Accuracy notes and limits
The Epley, Brzycki and Lombardi equations were fitted mostly at low rep counts. They diverge sharply above about 10 reps and tend to over-estimate there. They also differ by exercise — a squat and a bench press do not follow the same curve — and they assume a set taken close to failure with consistent technique. Use the estimate to guide training loads, not as a substitute for a supervised, properly warmed-up max attempt. This is an educational reference, not coaching advice.
Frequently asked questions
Which one-rep max formula is most accurate?
None is universally best. Epley and Lombardi read slightly higher than Brzycki at moderate reps, and the gap widens as reps rise. Showing all three — and their spread — is more honest than trusting one number, which is why this tool displays the range.
What is 80% of my one-rep max?
Multiply your 1RM by 0.80. For a 116 kg 1RM that is about 93 kg — a load most people manage for roughly 8 reps. The training-load table above lists the common percentages and the weights and rep counts they map to.
How many reps is 90% of a one-rep max?
About 3–4 reps for most trained lifters. Rep-to-percentage figures are typical ranges, not fixed rules — the exact number varies by exercise, training history and how close to failure you push.
How many reps should I use for the estimate?
Fewer is better. A set of 1–5 reps close to failure is most reliable; beyond about 10 reps the formulas diverge and over-estimate. To compare strength across bodyweights instead, use a scoring formula like Wilks or IPF GL points.
How often should I re-test my one-rep max?
For most lifters, re-estimating every 4–8 weeks — or at the end of a training block — is plenty. Testing more often adds fatigue without giving your program time to produce a real change.
Related tools and reading
How to estimate your one-rep max
The three formulas explained, with worked numbers and where each breaks down.
Wilks calculator
Compare total strength across bodyweights with the published Wilks coefficient set.
Sources
- One-repetition maximum — formula reference — consolidates the Epley, Brzycki and Lombardi equations and the reps-to-percentage relationship used on this page. Checked 24 Aug 2026.
- Epley, B. (1985). Poundage Chart. Boyd Epley Workout, University of Nebraska — origin of the Epley equation.
- Brzycki, M. (1993). Strength testing — predicting a one-rep max from reps to fatigue. JOPERD, 64(1), 88–90 — the Brzycki equation.
- Lombardi, V.P. (1989). Beginning Weight Training. Wm. C. Brown — the Lombardi equation.
- Percentage-based training loads follow the widely used strength-training intensity continuum; working weights in the table were computed by ScoreIndexer from a 116 kg example 1RM.