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# 1RM Calculator

This 1RM (one repetition maximum) calculator provides estimates, according to seven different equations, of the maximum amount of weight you would be able to lift only once for any given resistance exercise. Although it is possible to determine your 1RM through trial and error, it is generally not advisable for safety reasons. If you want to know the heaviest weight you would be able to lift for a given exercise, a 1RM calculator is a safe and reliable alternative to an actual attempt of a maximum lift. Note that you can use this 1RM calculator for any type of lift. There is no specific 1RM formula for deadlift, squat, bench press, etc. This calculator accurately determines your 1RM for any and all resistance exercises.

1RM Calculator

Instructions
To calculate your 1RM select a weight that you predict you can lift up to a maximum of 10 repetitions and perform a set with this chosen weight, completing as many repetitions as you can until failure (i.e. continue lifting until you can no longer lift the weight with proper form) without exceeding 10 repetitions. If you exceed 10 repetitions before failure then, after resting for 10 minutes, try a heavier weight such that you fail before or at 10 repetitions. When you are finished enter the amount of weight you lifted and the number of repetitions you completed into the 1RM calculator below.

Weight Lifted

Repetitions Completed

Note
This 1RM calculator is considered to be reasonably accurate for entries of up to 10 repetitions. The calculator will not determine your 1RM for entered repetition values of greater than 10. Also note that this 1RM calculator should be treated only as a rough prediction tool, and its accuracy will vary depending on a large number of factors, one of which is the resistance training experience of the user. In general, a 1RM calculator will return more accurate results for an experienced weightlifter.

## Reliability

How reliable are the estimates of a 1RM calculator, you ask? Well, the 1RM calculator equations used for the calculator above have been experimentally shown to predict 1RM to within roughly 5% of actual achieved 1RM values for both bench press and squat, and to within roughly 10% of actual achieved 1RM values for deadlift.

## Equations

This 1RM calculator returns predictions of 1RM based on the seven equations described below:

• Brzycki: 1RM = W x (36 / (37 - R))

• Epley: 1RM = W x (1 + 0.0333 x R)

• Lander: 1RM = (100 x W) / (101.3 - 2.67123 x R)

• Lombardi: 1RM = W x R0.1

• Mayhew et al.: 1RM = (100 x W) / (52.2 + (41.9 x e-0.055 x R))

• O'Conner et al.: 1RM = W x (1 + 0.025 x R)

• Wathan: 1RM = (100 x W) / (48.8 + (53.8 x e-0.075 x R))

where

1RM = One Repetition Maximum
W = Weight Lifted
R = Repetitions Completed
e = Euler's Number = 2.71828 (approximately)

LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1RM performance in the bench press, squat, and deadlift. J Strength Cond Res. 1997. 11(4):211-13.