One Rep Max Calculator
Estimate a 1RM from weight lifted and reps completed.
Runs in your browser. Nothing is uploaded — your input is processed on this device and discarded when you close the tab.
One Rep Max Calculator
How to use this tool
- Enter the weight you lifted and how many reps you completed.
- Press Generate to see the estimated one-rep max.
- Try a different set to compare estimates across lifts.
Worked example
Lifting 100 for 5 reps gives an estimated one-rep max of 100 x (1 + 5 / 30) = 116.67, using the Epley formula.
What this tool does not do / Limits
This is an estimate from the Epley formula, 1RM = weight x (1 + reps / 30). It is not a training prescription, it is less reliable above about 10 reps, and it does not account for technique, fatigue or body weight.
Frequently asked questions
What is the Epley formula?
It estimates a one-rep max as weight multiplied by one plus reps divided by 30.
Why is the estimate less reliable for high reps?
Endurance plays a bigger part as reps rise, so a high-rep set says less about a single maximum effort.
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