One rep max (1RM) calculator
It lets you gauge your max strength on a lift such as the bench press or squat without risking a true max attempt.
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How to use it
- Enter weight lifted (kg or lb) and reps completed.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). With one rep the result is the weight itself.
Example
Inputs: Weight lifted (kg or lb) = 80, Reps completed = 8. Result: Estimated 1RM (average): 100.3; Epley formula: 101.3; Brzycki formula: 99.3.
Limits and caveats
- Estimates are more accurate at 10 reps or fewer and less so as reps rise.
- The formulas are estimates and vary by lift and muscle fiber type.
- Do not attempt a true max without a spotter and a proper warm up.
Questions about this tool
What is a 1RM?
The heaviest weight you can lift once with good form. It is the base for percentage-based training programs.
Which is more accurate, Epley or Brzycki?
They match exactly at 10 reps, and Brzycki gives slightly lower values at low reps, so the tool shows their average.
Should I use kg or lb?
Either one. The result comes out in the same unit you entered.