Maximum Repetitions Calculator
Estimate your one-rep max (1RM) from a submaximal lift, and see recommended training loads for every rep range.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
This tool provides general educational estimates only and is not medical advice. It does not diagnose, treat, or replace guidance from a qualified healthcare provider. Consult a doctor for decisions about your health.
About the Maximum Repetitions Calculator
The maximum repetitions calculator estimates your one-rep max (1RM) — the heaviest weight you could lift once — from a set of several repetitions. It averages two widely used prediction formulas, Epley and Brzycki, which are most accurate between about 2 and 10 reps. Knowing your estimated 1RM lets you set training weights as a percentage of maximum without the injury risk of testing a true single. The tool also lists working weights for common percentages.
How to use it
- 1Enter the weight you lifted.
- 2Enter how many clean repetitions you completed with it.
- 3Press Calculate to see your estimated one-rep max and training loads.
Worked example
lifting 100 kg for 5 repetitions gives 116.7 kg with the Epley formula and 112.5 kg with Brzycki, an average estimated 1RM of about 114.6 kg.
How it works
Formulas
Epley: 1RM = w × (1 + reps/30)
Brzycki: 1RM = w × 36 / (37 − reps)
We average the two for a balanced estimate.
Who it is for
Strength athletes, powerlifters and anyone following a percentage-based training programme.
Why it helps
It provides a working 1RM without a maximal attempt, which is safer and less fatiguing.
Common use cases
- Setting weights for a programme written in percentages of 1RM
- Tracking strength progress between test days
- Comparing strength across lifts
Common mistakes to avoid
- Using a set of more than 10–12 reps, where prediction errors grow quickly.
- Entering reps from a set that ended in poor form.
Frequently asked questions
A:Estimates are most accurate with 1–10 reps; above that error increases.
A:Maximal lifts carry injury risk. Estimating from submaximal sets is safer.
Reviewed for accuracy · Last updated October 7, 2026
Formulas follow recognised clinical references — including WHO BMI classifications, the Mifflin-St Jeor equation, and Naegele’s rule — and are periodically checked against published reference values.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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