Estimate the weight you could lift once, from a set you actually did — without attempting a true max. There are seven well-known formulas for this and they disagree with each other, sometimes by more than five percent, so this calculator runs all of them and gives you the range rather than pretending a single number is the answer. Every formula shows its equation so you can check it. Above ten reps you get told the estimate is losing accuracy, and above fifteen that these formulas have stopped being useful at all. Then the practical half: a percentage table with the weight for each training intensity, optionally rounded to plates you can actually load. Kilograms or pounds, and everything is calculated in your browser.
This tool does not use any data storage or network traffic.
Enter a weight and a rep count to estimate your one rep max.
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Every formula
| Formula | Equation | Estimate |
|---|
Training percentages
| Intensity | Weight | Typical reps |
|---|
The rep figures are the conventional rules of thumb, not measurements — how many reps you get at a given percentage varies a lot by lift, by training age and by person.
Nothing leaves your browser
Every estimate is calculated on this page. Nothing is uploaded, nothing is stored, and reloading the page clears it all.