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One-rep max calculator

Short answer: enter the set weight in kilograms and how many times you lifted it — the calculator shows an estimated one-rep max from seven recognised formulas, the median of the estimates and the working range. The calculation runs right in your browser and nothing is sent anywhere.

Worked example

Set 100 kg × 5 reps → median 116.5 kg The values match the formulas below — you can check them by hand.

Calculate your 1RM

Units
For example 72.5. Accepted from 1 to 500 kg.
How many times you lifted this weight: a whole number from 1 to 10.

How to use the calculator

  1. Pick the exercise and the weight you performed the set with to failure (or close to failure).
  2. Enter the weight in kilograms — halves are allowed, for example 72.5.
  3. Enter how many times you lifted that weight (from 1 to 10).
  4. Press "Calculate".

The result is the median of the seven formula estimates and the working range. The median is steadier than a single formula: the formulas look at the same set differently, and the median smooths the extremes.

Where the formulas come from

The calculator uses a set of seven widely used equations, collected and compared in the validation study by LeSuer and colleagues (1997): Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, Wathen. The equations describe a linear or exponential relationship between reps to failure and the share of the maximum. At one repetition every formula returns the set weight itself — the only case where the maximum is known without estimation.

How to check it by hand

Set: 100 kg × 5 reps. The expected calculator result is a median of 116.5 kg and a range of 112.5–119.0 kg. You can check it by hand with any formula, for example Epley: 100 · (1 + 5/30) = 116.7 kg (shown as 116.5 kg after rounding to 0.5 kg). The Brzycki formula gives 100 · 36 / (37 − 5) = 112.5 kg.

Limitations

  • An estimate does not replace a measurement: the difference from your real maximum can reach 10 % or more.
  • The more reps in the set, the lower the accuracy. The input range is limited to 1–10 repetitions.
  • The result is not an instruction to go and test your maximum: a real 1RM test needs a spotter and preparation.

Author

FitTop editorial team — Site editorial team

FitTop is an independent project. Editorial material is separated from advertising and partnership elements. The editorial team does not give individual medical advice; for health questions, see a doctor or a qualified specialist.

Sources and review date

  1. The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift — Journal of Strength and Conditioning Research, 1997-11-01. Supports: The composition of the formula set (Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, Wathen) and a comparison of their accuracy for the bench press, squat and deadlift.
  2. Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue — Journal of Physical Education, Recreation & Dance, 1993-03-01. Supports: The Brzycki formula; the rationale for estimating a maximum from reps to failure.
  3. Prediction of One Repetition Maximum Strength From Multiple Repetition Maximum Testing and Anthropometry — Journal of Strength and Conditioning Research, 2006-05-01. Supports: The error of submaximal 1RM estimates compared with a direct measurement — the basis for the accuracy warning.
  4. One-repetition maximum (reference article: Epley formula, Epley 1985 "Poundage Chart") — Wikipedia. Supports: The Epley formula w·(1 + r/30); cited from the reference article.

Formula version:1rm-multi-est-v1. Last reviewed: September 2, 2026