What is a one-repetition maximum?
A one-repetition maximum is the greatest load you can lift for one technically sound repetition in a specific exercise. An estimate is calculated from a submaximal performance rather than directly tested.
Useful calculators
One-Rep Max Calculator
Estimate your one-repetition maximum (1RM) using a weight you’ve lifted for a known number of repetitions.
Your estimated 1RM can help you understand your current strength and explore percentage-based training loads without needing to perform an actual maximal lift.
Results are estimates and may differ from your true maximum.
Percentage-based loads
Explore estimated training loads
These are starting points, not guarantees of how many repetitions you can complete. Practical loads are rounded to the nearest 2.5 kg; equipment and exercise choice may require a different increment.
| Percentage | Calculated load | Practical 2.5 kg load |
|---|---|---|
| Enter a valid set to see estimated loads. | ||
2. Understand your results
What an estimated 1RM can tell you
Why use an estimate?
An estimated 1RM can help you track strength and explore relative training loads without needing to perform a true maximum. It should be compared within the same exercise and similar conditions.
Why estimates vary
Technique, fatigue, exercise choice, training experience and proximity to failure all affect the estimate. Predictions become less reliable at higher repetition counts and are not equally accurate for every person or exercise.
3. How to apply this
How to use percentage-based loads
Percentage-based loads can provide a useful starting point when planning strength training. Begin with appropriate warm-up sets, keep technique consistent and adjust based on your actual performance.
Percentages are guides, not guarantees of a particular repetition number. Your capacity can vary between exercises, sessions and levels of fatigue, so a calculated load should never replace sensible judgement.
You do not need to test a true maximal lift to use this tool. Do not attempt maximal lifts when you are inexperienced, injured or unable to perform the exercise safely; use suitable supervision where needed.
4. Method and further reading
How this is calculated
This calculator uses the Epley equation: Estimated 1RM = weight lifted × (1 + repetitions ÷ 30).
For example, 100 kg lifted for five repetitions gives an estimated 1RM of 116.7 kg. One repetition returns the entered weight rather than adding a formula-based increase.
The Epley equation is a predictive formula, not a direct measurement. It originated as a practical coaching formula and should not be assumed equally accurate for every exercise or repetition range. For context on 1RM measurement and prediction, see this critical review of maximal-strength measurement methods.