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.
- 2 cited sources
- Calculates in your browser
Your answer
Appears here as you enter your details. No demo figures — the number is yours, or it is nothing.
Baseline
Know all your numbers
BMI, resting rate, daily burn, eating target, macros, body fat, waist ratios, heart-rate zones and your fitness age: 15 in all. Answer once, see them together, and stop whenever you like.
Get my Baseline →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 to 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 to 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 to 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, and 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.
Embed this calculator
Free to embed with the attribution link intact.
<iframe src="https://www.tools.fit/embed/one-rep-max-calculator" width="440" height="420" style="border:0;max-width:100%" title="Calculator by FitTools" loading="lazy"></iframe>Related tools
- Keep this number
A free account puts this number on a home screen with the rest of yours, on every device you sign in on. One tap, no password.
- Gym tracker: log sets, reps and weights
Put these numbers to work: a free workout log in your browser, with last session beside every set. Free account keeps it, and signing up is one tap.
- Barbell Plate Calculator: Load the Bar Right
Free barbell plate calculator: enter a target weight and bar, edit your plate inventory, and get the per-side stack or the nearest achievable load.
- Strength Standards: How Strong Are You, Really?
Free strength standards tool: rank your squat, bench press and deadlift from untrained to elite using Kilgore's published tables, with your powerlifting total and the exact kg to your next tier.
- DOTS Calculator: Wilks & IPF GL Points
Free DOTS calculator with Wilks and IPF GL points, using official OpenPowerlifting coefficients, regression-tested against real meet results.
- CrossFit Benchmark Calculator: Rank Your Fran, and Every Girl WOD
Free CrossFit calculator: rank your Fran, Grace, Helen, Filthy Fifty or Fight Gone Bad against published normative data, plus every Girl WOD with prescribed weights in lb and kg.