One Rep Max Calculator
Estimate the maximum weight you could potentially lift for one repetition based on the weight and repetitions you can currently perform.
Calculate your one rep max
Enter the weight you lifted and the number of repetitions you completed to estimate your 1RM.
Your result
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| Weight lifted | — |
| Repetitions | — |
| Estimated one rep max | — |
| Estimated 1RM in kg | — |
| Estimated 1RM in lb | — |
Step-by-step calculation
What does the result mean?
Your one rep max, or 1RM, is an estimate of the maximum weight you could lift for one complete repetition of an exercise.
A 1RM calculator allows you to estimate your maximum strength without necessarily attempting a true maximum lift.
The estimate becomes less reliable as the number of repetitions increases. For this reason, this calculator accepts up to 10 repetitions.
How is one rep max calculated?
This calculator uses the Epley formula. The formula estimates one rep max from the weight lifted and the number of repetitions completed.
For example, if you lift 80 kg for 5 repetitions, the formula increases the lifted weight according to the additional repetitions performed.
The result is an estimate of maximum strength and should not be interpreted as a guaranteed maximum lift.
One rep max example
Suppose you can lift 80 kg for 5 repetitions.
Estimated 1RM = 80 × (1 + 5 ÷ 30)
Estimated 1RM = 80 × 1.1667
Estimated 1RM = 93.3 kg
Your estimated one rep max would therefore be approximately 93.3 kg.
Formula used
This is the Epley equation. Different 1RM equations can produce slightly different estimates, so the result should be used as a training reference rather than an exact measurement.
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Important: This calculator provides an estimated one rep max for general informational and training purposes only. The calculated value is not a guarantee of the amount of weight you can safely lift. Attempting a true maximum lift can increase the risk of injury, particularly when performed without proper technique, equipment, supervision, or appropriate preparation. Use appropriate safety precautions and consult a qualified fitness or healthcare professional if you are unsure whether maximum-effort lifting is suitable for you.