JLJosh Liljenquist

Strength estimate calculator

One rep max calculator

Estimate a one-repetition maximum from one completed set. The tool shows both Brzycki and Epley predictions so the difference between established formulas stays visible instead of presenting one estimate as exact.

By

Two formulasRange shownEstimate only

Enter known values

Enter the known values and select Calculate.

How to use this calculator

  1. Choose the lift label for your own record; it does not change the formula.
  2. Enter the external weight and completed repetitions from one set.
  3. Use a low-repetition set that reflects consistent technique.
  4. Read the formula range rather than treating the midpoint as a guaranteed result.

Formula and method

Brzycki: 1RM = weight × 36 ÷ (37 − reps). Epley: 1RM = weight × (1 + reps ÷ 30). The displayed midpoint is the average of those two estimates.

Worked example

For 185 lb completed for 5 repetitions, Brzycki estimates about 208.1 lb and Epley estimates about 215.8 lb. The spread illustrates why the output is a prediction, not a measured maximum.

Assumptions and result interpretation

  • The equations estimate performance and can vary by exercise, experience, fatigue, technique, and individual response.
  • Repetitions are limited to 1–12 because predictions become less informative as the set moves farther from a maximum.
  • The tool does not account for body mass in pull-ups or dips.
  • This page is not medical, injury-prevention, or individualized training advice.

Understanding the result

An estimated maximum is most useful as a consistent reference point. Comparing estimates made with similar exercises, rep ranges, technique, and conditions is usually more meaningful than comparing unrelated sets.

Common mistakes

  • Adding repetitions across multiple sets
  • Using assisted or partial repetitions without noting the difference
  • Treating the estimate as a required attempt
  • Comparing different exercises as though formula accuracy is identical

Methodology sources

This calculator owns a distinct job in the current collection. Additional related tools will be linked only when they are genuinely useful.

Browse all calculators.

Use this result as a calculation aid. Confirm input definitions, required precision, and any governing policy or professional standard separately.