How to use the one rep max calculator
- Type the Weight lifted for a hard set, as a plain number such as 185 or 82.5.
- Type the Reps completed in that set, a whole number from 1 to 20. Sets of 2 to 10 reps that end close to failure work best.
- Choose the Unit, lb or kg, and enter the weight in that unit.
- Read the average estimate and the three formula results. The table turns your 1RM into training loads from 100% down to 50%.
How the three formulas work
Each formula predicts the weight you could lift once from a set of several reps, where w is the weight lifted and r is the number of reps:
- Epley (1985): 1RM = w × (1 + r / 30)
- Brzycki (1993): 1RM = w × 36 / (37 - r)
- Lander (1985): 1RM = 100 × w / (101.3 - 2.67123 × r)
The large number is the average of the three, taken before rounding. With 1 rep every result equals the weight you lifted, since that is a tested max. LeSuer and colleagues (1997) compared the equations. The typical reps column and training ranges come from the NSCA training load chart.
Worked example
The starting inputs are 185 lb for 5 reps. Epley gives 185 × (1 + 5 / 30) = 215.8 lb, Brzycki gives 185 × 36 / 32 = 208.1 lb, and Lander gives 18,500 / (101.3 - 13.356) = 210.4 lb. The tool shows these as 216, 208 and 210 lb, and shows the average of the unrounded values, 211.4 lb, as 211 lb. In the table, 90% is 190 lb, 80% is 169 lb and 70% is 148 lb.
Limits and edge cases
Above 10 reps the three formulas drift apart, so the tool shows a warning there and rejects more than 20 reps. They were tested on the squat, bench press and deadlift, and in that study every equation underestimated the deadlift, so treat other lifts as rough guides. A tested max needs warm-up sets, good form and a spotter, which is why many lifters prefer an estimate from 3 to 5 reps. Related tools: the weight converter switches pounds and kilograms, the macro calculator sets protein for strength training, and the lean body mass calculator shows how much of your weight is not fat.
Frequently asked questions
How accurate is a one rep max calculator?
It is an estimate, not a measurement. The formulas can be off by 10 percent or more for some lifters, and in a study of 67 college students every equation underestimated the deadlift by 9 to 14 percent. Sets of 10 reps or fewer give the best results.
How many reps should I use to estimate my 1RM?
Use a hard set of 2 to 10 reps that ends close to failure, and 3 to 5 reps if you can. The formulas drift apart above 10 reps, so this tool warns you there and stops at 20 reps.
Why do the three formulas give different answers?
Each was fitted to a different group of lifters. For 185 lb and 5 reps, Epley gives 216 lb, Brzycki 208 lb and Lander 210 lb, so the calculator averages them to soften the bias of any single formula.
What percentage of my 1RM should I train with?
The NSCA lists 85 percent or more with 6 or fewer reps for strength, 67 to 85 percent for 6 to 12 reps for muscle size, and 67 percent or less for 12 or more reps for endurance. The table under the result turns those percentages into weights.
Sources: LeSuer et al. 1997; Brzycki 1993; NSCA training load chart; Epley and Lander (1985), as cited by LeSuer. General estimates, not medical advice.