One Rep Max Calculator

One Rep Max – Quick Cheat Sheet

1RM = your max load for a single rep. This tool estimates 1RM from a submax set.
Inputs: working weight and reps. Choose lb or kg. Optional plate rounding to match your gym plates.
Formulas included: Epley, Brzycki, Lombardi, O’Conner, Mayhew (bench), Wathan. Average is reported plus a “training max” (90%).
Rep range: Use 1–12 reps for best accuracy; higher reps increase uncertainty.
Percent table: Common training loads (95–50% of 1RM) based on the average estimate.
Rounding: Round to 2.5 kg or 5 lb (or your choice) to produce plateable numbers.
Safety: Always warm up and use proper form/spotter. Numbers are estimates, not prescriptions.

Formula notes

Epley = w × (1 + r/30), Brzycki = w × 36/(37 − r)
Lombardi = w × r^0.10, O’Conner = w × (1 + 0.025r)
Mayhew = 100w / (52.2 + 41.9e^−0.055r), Wathan = 100w / (48.8 + 53.8e^−0.075r)
All formulas are unit-agnostic; inputs/outputs follow your unit selection.