RapidRatio

One Rep Max Calculator

Enter Lift Data

Estimates are most accurate for 10 or fewer repetitions.

Results

Estimated 1RM (Epley) —
Brzycki Formula —
Lander Formula —
O'Conner Formula —
Lombard Formula —

How One Rep Max is Estimated

Your one-repetition maximum (1RM) is the maximum amount of weight you can lift for a single repetition of an exercise. Directly testing your 1RM can be dangerous, so strength coaches use predictive formulas.

The Estimation Equations

Let $w$ represent the weight lifted and $r$ represent the number of repetitions completed:

  • **Epley:** $1\text{RM} = w \times (1 + r / 30)$
  • **Brzycki:** $1\text{RM} = w / (1.0278 - 0.0278 \times r)$
  • **Lander:** $1\text{RM} = (100 \times w) / (101.3 - 2.67123 \times r)$
  • **O'Conner:** $1\text{RM} = w \times (1 + r / 40)$
  • **Lombard:** $1\text{RM} = w \times r^{0.10}$
Disclaimer. 1RM calculations are estimates. Muscle group recruitment, training experience, muscle fiber distribution, and form can cause actual max lifting capacities to vary. Always use a spotter when lifting heavy weights.