One Rep Max Calculator

Estimate the maximum weight you can lift for a single repetition from a sub-maximal set using Epley, Brzycki, and other formulas.

The formula this calculator uses

One Rep Max Calculator

Epley: 1RM = w × (1 + r/30)
Brzycki: 1RM = w × 36 / (37 − r)
Lombardi: 1RM = w × r^0.10

Example: 100 kg × 5 reps → ~116–120 kg estimated 1RM

Why estimate 1RM?

Knowing your approximate one-rep max lets you prescribe training percentages (e.g. 80% of 1RM for strength work) without the fatigue and risk of frequent maximal testing.

How to use this calculator

  1. Enter the required values in the fields above.
  2. Results update automatically as you type.
  3. Adjust any input to explore different scenarios.

Frequently asked questions

How accurate are 1RM formulas?

They are good estimates (±5–10%) for reps in the 2–10 range. Accuracy falls for very high rep sets.

Should I actually test a true 1RM?

Only with proper warm-up, spotters, and experience. Sub-maximal estimates are safer for most trainees.

Which formula is best?

Epley and Brzycki are the most widely used. Averaging several formulas often gives a balanced result.

Can I use this for any lift?

Yes for compound lifts (squat, bench, deadlift, overhead press). Isolation exercises are less reliable.