One-Rep Max Calculator
Estimate an exercise-specific one-repetition maximum from a 1–10-rep set with Brzycki and Epley equations.
Content updated August 7, 2026
A repetition equation estimates an exercise-specific 1RM; it does not measure it. Technique, fatigue, equipment and training status affect the result. Do not attempt a maximal lift without suitable skill, setup and supervision.
A one-repetition maximum is the heaviest load completed once for a particular exercise and technique. This calculator estimates it from a submaximal set using both Brzycki and Epley equations, then shows their average and range.
Enter a technically consistent set of 1–10 repetitions completed close to fatigue. The result belongs to that exercise and setup; it is not a general measure of strength and does not require you to attempt a maximal lift.
The One-Rep Max formula
Brzycki: 1RM = W × 36 ÷ (37 − R); Epley: 1RM = W × (1 + R ÷ 30)W is the completed load and R is a whole number of repetitions from 1 to 10. At R = 1, this calculator returns W exactly for both equations.
Worked example
For 80 kg completed for 5 reps, Brzycki estimates 90.00 kg and Epley estimates 93.33 kg. Their displayed average is 91.67 kg, with both source estimates retained.
Assumptions, rounding, and limitations
Assumptions
- The repetitions form one technically consistent set completed close to fatigue.
- The load, equipment, exercise and range of motion remain specific to the estimate.
- The entered repetition count is a whole number from 1 through 10.
Rounding: The engine retains full precision. Loads are displayed with up to two decimal places and conversions use one pound = exactly 0.45359237 kilogram.
Limitations
- Repetition formulas estimate rather than measure 1RM and can disagree with an actual maximum.
- Technique, fatigue, training status, exercise selection and repetitions in reserve affect accuracy.
- The result is not a training prescription and does not establish that a maximal attempt is safe.
Sources
- The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift — Journal of Strength and Conditioning Research
- Muscular endurance repetitions to predict bench press strength in men of different training levels — PubMed / Journal of Sports Medicine and Physical Fitness
Why two equations are shown
Brzycki and Epley apply different curves as repetitions increase. Their answers are usually close at low repetitions but can diverge, so displaying both exposes formula uncertainty instead of presenting one estimate as a measurement.
When one repetition is entered, the completed load is returned exactly for both equations. For two through ten, the average is a convenient summary while the individual values remain visible.
Keep the estimate exercise-specific
Bench press, squat, deadlift and machine movements have different technique, range of motion and fatigue patterns. A set performed on one movement should not be used to infer a maximum on another.
Prediction error also changes with training status and the repetitions actually remaining at the end of the set. Use the same setup and technique when comparing estimates over time.
Frequently asked questions
▶How does the calculator estimate 1RM?
It applies the Brzycki and Epley repetition equations to the entered load and reps, then shows both results, their range and their average.
▶Why is the calculator limited to 10 repetitions?
Prediction error tends to grow as sets get longer, and published validation work cautions against extending common repetition equations far beyond ten reps.
▶What happens if I enter one repetition?
A successfully completed single is already a one-repetition result for that set, so both equations return the entered load exactly.
▶Can I use the result for another exercise?
No. Treat it as specific to the exercise, equipment, range of motion and technique used for the entered set.
▶Should I test the estimated maximum?
The estimate does not require a maximal attempt. Maximal lifting adds risk and should only be considered with suitable experience, equipment, setup and supervision.
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Open calculator →Disclaimer: One-Rep Max Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.