Health & Fitness
One-Rep Max Calculator
Updated Aug 26, 2026 Reviewed Aug 26, 2026
Estimate one-repetition maximum with seven equations, compare model range, and build rounded percentage training loads.
Strength estimate and load planning
Enter a completed set
Result
Calculation summary
Enter values to see the result
Your result, breakdown, assumptions, and warnings will appear here.
Live strength preview
Estimated maximum and working loads
Predicted 1RM = selected equation(load, repetitions)
- Selected 1RM
- 92.4 kg
- Equation range
- 90–95.2
- Rounded 80%
- 75 kg
How to use this calculator
- 1Enter the heaviest load completed for one continuous set and the repetitions performed.
- 2Choose one equation or the transparent average of all equations.
- 3Review the range and open a rounded target in the plate calculator.
Formula
predicted 1RM = f(load, repetitions)
Epley, Brzycki, Lander, Lombardi, Mayhew, O’Conner and Wathan equations are evaluated; Average is their arithmetic mean.
Calculation steps
- Validate a set of 1–12 repetitions.
- Evaluate all included equations and select the requested method.
- Multiply the estimate by each percentage and round to the equipment increment.
Worked example
A set of 80 kg for five repetitions produces estimates in the low-to-mid 90 kg range, depending on the equation.
Assumptions
- The set used consistent technique and range of motion.
- Predictions are specific to the exercise.
- Higher repetitions add uncertainty.
- The result does not assess safety or readiness.
Sources
Frequently asked questions
Why do equations disagree?
They were fitted from different populations, exercises and repetition ranges; the range exposes that uncertainty.
Which method should I use?
Use one consistently when tracking change; Average is useful when no exercise-specific choice has been made.
Why stop at 12 repetitions?
Prediction uncertainty grows as the set moves farther from a true maximum.
Should I test the estimate immediately?
Not automatically; training experience, technique, fatigue, equipment, spotting and health all matter.
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