One Rep Max Calculator
This one rep max calculator estimates the most weight you could lift for a single repetition from a set you have performed, averaging the Epley, Brzycki and Lombardi formulas, and shows a percentage chart for planning training loads.
About this tool
This one rep max calculator estimates the most weight you could lift for a single repetition from a set you have performed, averaging the Epley, Brzycki and Lombardi formulas, and shows a percentage chart for planning training loads.
How to use it
- Enter the weight you lifted in kg or lbs.
- Enter how many clean reps you performed.
- Read your estimated 1RM and the result from each formula.
- Use the percentage chart to pick working weights for your target rep range.
Good to know
- Epley: 1RM = weight × (1 + reps ÷ 30).
- Brzycki: 1RM = weight × 36 ÷ (37 − reps).
- Lombardi: 1RM = weight × reps^0.10; the estimate shown is the average of the three.
- Estimates are most accurate between 2 and 10 reps and become less reliable above 10.
- The chart maps percentages of 1RM to typical rep ranges, for example about 80% for 7–8 reps.
Runs entirely in your browser — nothing you enter is uploaded or stored.
Frequently asked questions
What is a one rep max?
Your one rep max (1RM) is the heaviest weight you can lift for a single repetition with good form. It is used to set training loads as percentages, such as 75% of 1RM.
How accurate are 1RM calculators?
They are usually close for sets of 2–10 reps, but individuals vary with training history and exercise. An estimate from a set of 3–5 reps is generally more accurate than one from 12 or more.
Is it safe to test my real one rep max?
True max attempts carry more injury risk and need a spotter, good technique and a proper warm-up. Estimating from a submaximal set avoids that risk.
Which formula is best — Epley or Brzycki?
They give very similar results at low reps; Brzycki tends to be slightly lower as reps increase. Averaging several formulas, as this calculator does, smooths out their differences.