One-Rep Max Calculator — Epley, Brzycki & More
Estimate your one-rep max from any set of ten reps or fewer, with a working-weight percentage table.
- Strength
- 2 cited sources
- Runs in your browser
Your estimated one-rep max
116.7 kg
An estimate, not a guarantee — individual rep-to-max relationships vary by lift and lifter. Use it to set training percentages rather than to attempt a true max.
| % of 1RM | Weight |
|---|---|
| 50% | 58.3 kg |
| 55% | 64.2 kg |
| 60% | 70.0 kg |
| 65% | 75.8 kg |
| 70% | 81.7 kg |
| 75% | 87.5 kg |
| 80% | 93.3 kg |
| 85% | 99.2 kg |
| 90% | 105.0 kg |
| 95% | 110.8 kg |
Methodology
The calculator estimates a one-repetition maximum from a submaximal set
using four published equations, where w is the weight lifted and r the
reps completed:
| Formula | Estimated 1RM |
|---|---|
| Epley (default) | w × (1 + r ÷ 30) |
| Brzycki | w × 36 ÷ (37 − r) |
| Lombardi | w × r^0.10 |
| O'Conner | w × (1 + 0.025 × r) |
Estimates are treated as valid for sets of ten reps or fewer — beyond that, the relationship between reps and maximal strength degrades and the tool warns you. The working-weight table converts your estimated max into loads at 50–95% in five-point steps, the percentages most programmes prescribe.
Interpreting your result
Prediction accuracy is genuinely good in the useful range: comparisons against tested maxima (LeSuer et al., 1997) found correlations above 0.95, with typical errors of a few percent for bench press and squat. Expect the formulas to agree closely for sets of 1–5 reps and drift apart as reps climb — at ten reps Epley and Brzycki converge, while Lombardi and O'Conner run lower.
The estimate's best use is programming: percentage-based training works perfectly well off an estimated max, without the fatigue and injury risk of testing a true single.
Limitations
- Rep-to-max relationships are individual: fibre type, training history and technique all shift where you fall against any formula.
- Accuracy varies by lift — published comparisons found deadlift maxima consistently underestimated, so calibrate per exercise.
- The set you enter must be honestly close to failure; a comfortable five-rep set predicts nothing about your maximum.
- An estimated 1RM is not a licence to attempt one. Maximal singles carry their own risk and belong in a structured programme with good technique.
Sources
Pull the receipts — 2 cited sources
FitTools · sources
- 01 LeSuer DA, et al. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res 1997;11:211–213
- 02 Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. JOPERD 1993;64:88–90
Every formula cited ✓
Frequently asked questions
- How accurate are 1RM calculators?
- For sets of ten reps or fewer, published comparisons find estimates typically land within a few percent of a tested max, with correlations above 0.95. Accuracy drops as reps rise, which is why this tool warns beyond ten reps.
- Which 1RM formula is best?
- Epley is the most widely used and is the default here. Brzycki tends to agree closely at low reps; differences between formulas grow with higher-rep sets, so we show the formula name with every estimate.
- Do I ever need to test my true 1RM?
- Not unless you compete in a strength sport. An estimated max is accurate enough for setting training percentages, without the injury risk and fatigue cost of a true maximal attempt.
- How do I use the percentage table?
- Most strength programmes prescribe working sets as a percentage of 1RM — for example 5 reps at 75–85%. Read your estimated max, then take the row for the percentage your programme calls for.
- Why does my estimate differ between exercises?
- Rep-to-max relationships vary by lift and by lifter — deadlifts in particular are commonly underestimated by prediction equations. Calibrate against how each lift actually feels rather than transferring one lift's estimate to another.
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<iframe src="https://tools.fit/embed/one-rep-max-calculator" width="440" height="420" style="border:0;max-width:100%" title="Calculator by FitTools" loading="lazy"></iframe>Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.
Last reviewed:
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