CalcArcade.

One Rep Max Calculator

Enter the weight you lifted and how many clean repetitions you did. You get three estimates of the heaviest weight you could lift once, their average and a percentage table.

Your numbers

Result

Estimate for information only, not professional advice. Last reviewed .

How we calculate it

Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). Lombardi: 1RM = weight × reps^0.10. With 100 kg for 5 reps the three give 116.7, 112.5 and 117.5 kg, and the average is 115.5 kg. One repetition is the weight itself.

The table shows the average estimate multiplied by each percentage from 100% down to 50%, rounded to one decimal.

Assumptions and limits

  • This is an estimate for general information. It is not medical advice and cannot replace a conversation with a doctor or dietitian. Do not attempt a true one rep max without a spotter, good form and a warm up.
  • The formulas are less accurate above about 10 repetitions, so the calculator accepts 1 to 15.
  • Results differ by exercise and by person, and the estimates are usually rounded to the nearest plate you have.

Frequently asked questions

What is a one rep max?

The heaviest weight you can lift for one repetition with good form. Estimating it from a lighter set avoids the risk of testing it directly.

Which formula is the most accurate?

None is exact. They agree closely for low reps and spread out as reps rise. The average smooths out the differences.

How do I use the percentage table?

Training plans often prescribe a percentage of your max. Find that row to see the weight to load.

Related calculators

Worked example (a fixed example using the starting numbers, it does not change as you type)

Inputs: Unit = Pounds; Weight lifted = 185; Repetitions (1 to 15) = 5.

  • Average (estimated 1RM) 213.8 lb
  • Epley 215.8 lb
  • Brzycki 208.1 lb
  • Lombardi 217.3 lb

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Last reviewed: . Formulas and assumptions are described on our methodology page. For information only; not professional advice.