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.
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.
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))
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.