One Rep Max Calculator
Estimate a one-repetition maximum from a completed set and view illustrative training percentages.
Your estimate
Enter your values and calculate. Results will appear here.
The estimate extrapolates from a repetition set. It is exercise-specific and depends on how close that set was to fatigue. A comfortable set with many repetitions left cannot establish a reliable maximum.
How to use this calculator
Enter the total external load, including the bar where applicable, and 1–10 repetitions from an already completed set. Use a consistent exercise and range of motion. You do not need to attempt a maximal lift to use this page.
Formula and methodology
Brzycki estimate = total load × 36 ÷ (37 − completed repetitions). Percentage load = estimated 1RM × percentage / 100.
Worked example
A completed set of 60 kg for five repetitions gives 60 × 36 ÷ 32 = 67.5 kg. The 80% row is 54 kg. That is an arithmetic percentage, not a command to lift a specific load.
What the result means
The estimate extrapolates from a repetition set. It is exercise-specific and depends on how close that set was to fatigue. A comfortable set with many repetitions left cannot establish a reliable maximum.
Limitations
Do not perform a dangerous set to improve the input. Beginners should use qualified supervision and appropriate safety equipment. Technique, fatigue and exercise choice affect the estimate. The table is illustrative, not a training prescription; round equipment loads conservatively.
Common mistakes
Do not enter the weight of just one plate when the input expects total load. Bodyweight movements and assisted machines may need a different model, so do not assume their displayed load is directly comparable.
Frequently asked questions
Why are more than ten repetitions rejected?
This tool deliberately limits extrapolation from high-repetition sets. It does not imply exact accuracy within the accepted range.
Should I try the estimated maximum?
No. An estimate is not clearance to attempt a maximum. Use safe, supervised training appropriate to your experience.