One-Rep Max Calculator
Estimate your one-rep max from a recent lift using multiple strength formulas. Compare estimated 1RM, training percentages, rep-max predictions, RPE adjustments and safe working weights.
Calculator
Use the working weight from your set.
Most formulas are most reliable from 1–10 reps.
10 = true max effort. 9 = about 1 rep left.
Using the average can smooth out formula differences.
Programme training max
Many strength programmes use a training max below true 1RM for safer loading.
Training percentage table
| % | Weight | Typical use |
|---|
Rep max prediction table
| Rep max | Estimated weight | % of 1RM |
|---|
Personalised guidance
How the one-rep max estimate works
A one-rep max is the maximum weight you could lift for one full repetition with good technique. This calculator estimates 1RM from a submaximal set using several common formulas.
Different formulas can give slightly different results, especially at higher rep counts. The average method combines several estimates to reduce the effect of any single formula.
The RPE adjustment estimates how many reps you may have had left. For example, a 5-rep set at RPE 9 is treated more like a 6-rep potential set because you likely had one rep in reserve.
Note: Estimated one-rep max values are not guaranteed. Technique, fatigue, warm-up, equipment, range of motion, exercise selection, bodyweight changes and confidence under heavy loads can all affect real performance.
Safe use of 1RM estimates
- •Use good technique first. A heavier estimated number is not useful if the original set had poor form.
- •Be cautious with high-rep estimates. Sets above 10 reps can become more conditioning-based and less accurate for 1RM prediction.
- •Use a training max. Programming from 85–90% of estimated 1RM often works better than using a true max every week.
- •Use spotters or safety bars. This is especially important for bench press and squat attempts.
- •Retest gradually. Add load in small jumps rather than jumping straight to the estimated max.