One-Rep Max Calculator — educational

Enter the weight you lifted and the number of reps you did (1–12), and see your predicted one-rep max (1RM) under six peer-reviewed formulas (Epley, Brzycki, Lombardi, Mayhew, O'Conner, Wathan), the unweighted mean, and a 1–12 rep-max table for training. The formulas are most reliable on compound lifts (squat, bench, deadlift, overhead press) for sets of 2–8 reps. Nothing leaves your browser.

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Predicted 1RM (mean)
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Range: — – — kg

Predictions by formula

Six peer-reviewed formulas, each applied to the same weight × reps. The mean is the unweighted average and the page's headline number; the range shows the spread.

Rep-max table

If your 1RM is the mean above, here's the weight to lift for 1–12 reps at the canonical training percentages. The percentages blend the NSCA and Prilepin conventions and are training targets, not a prescription.

Reps % of 1RM Weight

About the formulas

  • Epley (1985) — 1RM = w × (1 + r / 30). The most widely cited formula. Best for sets of 2–10 reps.
  • Brzycki (1993) — 1RM = w × 36 / (37 − r). Slightly more conservative than Epley; widely used in coaching contexts.
  • Lombardi (1989) — 1RM = w × r0.1. Power-curve form, gives a softer estimate at high rep counts.
  • Mayhew et al. (1992) — exponential, validated on the bench press. Tends to predict slightly higher 1RMs than the others.
  • O'Conner et al. (1989) — 1RM = w × (1 + 0.025r). The simplest of the six (linear in r).
  • Wathan (1994) — exponential, validated on the deadlift. Close to Epley across the 2–10 range.