acalculator

What is my one rep max?

Enter a weight and how many reps you did with it. The calculator estimates the most you could lift once, with two well-known formulas.

Your numbers

Units
1 to 10 reps. The estimate is best at 10 reps or fewer.
One rep max (Brzycki)
225 lb

Lifting 200 lb for 5 reps puts your estimated one rep max at 225 lb.

One rep max (Epley)
233.3 lb
Average of both
229.2 lb

One rep max (Brzycki): 225 lb. Lifting 200 lb for 5 reps puts your estimated one rep max at 225 lb.

How to calculate

Estimates the one-repetition maximum (1RM) from a weight lifted for 1 to 10 reps with the Brzycki and Epley equations, or the weight to use for a number of reps.

Example with the default inputs (Weight lifted 200 lb, Reps 5): Lifting 200 lb for 5 reps puts your estimated one rep max at 225 lb.

Formula: 1RM = weight × 36 ÷ (37 − reps) (Brzycki 1993); Epley (1985): 1RM = weight × (1 + reps ÷ 30).

  • The set went to failure: you could not have done one more rep with good form.
  • Reps are from 1 to 10. Both equations lose accuracy with more reps, and they were fit on lifts such as the bench press, squat and deadlift.
  • Brzycki gives exactly the weight lifted for 1 rep. Epley gives 1/30 more than the weight for 1 rep; that is how the equation is written.
  • The weight lifted and the one rep max are at most 2,000 lb (907 kg).

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Weight lifted 200 lb, Reps 5 gives One rep max (Brzycki) 225 lb, One rep max (Epley) 233.3 lb, Average of both 229.2 lb.Source: hand calculation in content.mdx: Brzycki (1993) 200 × 36 ÷ 32 = 225 lb = 102.06 kg; Epley (1985) 200 × (1 + 5 ÷ 30) = 233.3 lb = 105.84 kg; mean 229.2 lb
  2. Weight lifted 220.5 lb, Reps 10 gives One rep max (Brzycki) 293.9 lb, One rep max (Epley) 293.9 lb.Source: hand calculation in content.mdx: 100 × 36 ÷ 27 = 133.33 kg; 100 × (1 + 10 ÷ 30) = 133.33 kg
  3. One rep max (Brzycki) 220.5 lb, Reps 8 gives Weight lifted 177.6 lb.Source: hand calculation in content.mdx: weight = 100 × (37 − 8) ÷ 36 = 80.56 kg
  4. Weight lifted 297.6 lb, One rep max (Brzycki) 330.7 lb gives Reps 4.6.Source: hand calculation in content.mdx: reps = 37 − 36 × 135 ÷ 150 = 4.6

How it works

Your one rep max (1RM) is the most weight you can lift once with good form. The calculator estimates it from a set of 1 to 10 reps taken to failure.

Brzycki (1993), used to solve for any of the three values:

  • 1RM = weight × 36 ÷ (37 − reps)
  • weight = 1RM × (37 − reps) ÷ 36
  • reps = 37 − 36 × weight ÷ 1RM

Epley (1985), shown next to it:

  • 1RM = weight × (1 + reps ÷ 30)

The calculator also shows the mean of the two estimates. From 1 to 10 reps, Epley's estimate is never below Brzycki's, and they are equal at 10 reps.

Weights may be in pounds or kilograms (1 lb = 0.45359237 kg). The formulas do not depend on the unit.

Assumptions

  • The set went to failure with good form.
  • Reps are from 1 to 10. A solved rep count outside that range has no answer.
  • At 1 rep, Brzycki gives the weight lifted and Epley gives 1/30 more. Both are shown as written.
  • Weights are at most 2,000 lb (907 kg).

Worked examples by hand

200 lb for 5 reps. Brzycki: 200 × 36 ÷ (37 − 5) = 7,200 ÷ 32 = 225 lb (102.06 kg). Epley: 200 × (1 + 5 ÷ 30) = 200 × 1.1667 = 233.3 lb (105.84 kg). Mean: (225 + 233.3) ÷ 2 = 229.2 lb.

100 kg for 10 reps. Brzycki: 100 × 36 ÷ 27 = 133.33 kg. Epley: 100 × (1 + 10 ÷ 30) = 133.33 kg. The two agree at 10 reps.

The weight for 8 reps with a 100 kg max. weight = 100 × (37 − 8) ÷ 36 = 2,900 ÷ 36 = 80.56 kg.

How many reps 135 lb should allow with a 150 lb max. reps = 37 − 36 × 135 ÷ 150 = 37 − 32.4 = 4.6, so about 4 full reps.

Other questions people ask

How do I calculate my one rep max?

Lift a weight for as many good reps as you can (up to 10), then use a formula. Brzycki: 1RM = weight × 36 ÷ (37 − reps). Epley: 1RM = weight × (1 + reps ÷ 30). For 200 lb × 5 reps, Brzycki gives 225 lb and Epley 233 lb.

Which one rep max formula is most accurate?

No single formula is best for every lift and person. In a study of 67 untrained college students (LeSuer and others, 1997), seven equations all tracked the real 1RM closely (r above 0.95), but most had a small average bias, and all of them underestimated the deadlift. Brzycki and Epley agree exactly at 10 reps and differ most at about 3 to 5 reps.

Why use 10 reps or fewer?

Both formulas were built from sets of low to moderate reps. With more reps, endurance matters more than strength, and the estimate becomes less reliable. Brzycki recommended no more than 10 reps.

What weight should I use for a set of 8?

Enter your one rep max and 8 reps, and leave the weight empty. With Brzycki, weight = 1RM × (37 − reps) ÷ 36, so a 100 kg max suggests about 80.6 kg for 8 reps.

Is it safe to test a real one rep max?

A true max attempt is heavy and needs a warm-up, good technique and a spotter or safety bars. Estimating from a set of 3 to 10 reps is a common, lower-risk alternative.