Load from 1RM Percentage Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/8/2026
The working load is calculated with 1RM × target percentage. With a 1RM of 100 kg, targeting 80% of that maximum corresponds to 80 kg, a load generally sustainable for about 7 to 8 reps.
Explanation
Strength training programs often express a working load as a percentage of the 1RM (the maximum load liftable for a single rep) rather than directly in kilos, which lets the same program automatically adapt to each lifter's level. This calculator starts from an already known 1RM (calculated, for example, with our 1RM calculator) to find the load corresponding to a target percentage, as well as an estimate of the number of reps generally achievable at that load, using the inverse of the same Epley formula. These correspondences between percentage and number of reps remain average estimates: the actual relationship between load and maximum reps varies by exercise, individual, and fatigue level at the time, and many slightly different reference tables circulate in training literature. A high percentage (90% and above) is generally associated with developing maximum strength, a moderate percentage (65-80%) with muscle hypertrophy, and a lower percentage (50-65%) with muscular endurance — general benchmarks, not strict rules.
Example: a 100 kg 1RM, target of 80%
Inputs
1RM: 100 kg. Target percentage: 80%.
Calculation
Working load = 100 × 0.80 = 80 kg. Estimated reps = 30 × (100 ÷ 80 − 1) = 30 × 0.25 = 7.5.
Result
At 80% of 1RM (80 kg), about 7 to 8 reps are generally achievable.
Frequently asked questions
Why isn't the estimated number of reps a whole number?
Because it is a continuous mathematical estimate, not an exact empirical measurement. In practice, it is generally rounded to the nearest whole number (7.5 becomes 7 or 8 depending on context), keeping in mind that the actual number of achievable reps also varies with fatigue, technique, and the training day.
Why does the result show 0 estimated reps at 100% of 1RM?
This is a side effect of the Epley formula, originally designed to estimate a 1RM from several reps, not the exact reverse at the limit of a single rep: at 100% of the maximum load, the formula mathematically returns 0 'additional' reps rather than 1. In reality, 100% of 1RM does correspond to a single maximum rep, not zero — this result of 0 is a quirk of the mathematical model to interpret with this in mind, not a calculation error.
How do I use this calculator if I don't know my exact 1RM?
First use our 1RM calculator to estimate it from a load and a number of reps already performed, then enter that result into this calculator to get the working loads corresponding to different percentages.
Are these percentages the same for all exercises?
The general relationship between percentage of 1RM and number of reps stays broadly similar across exercises, but it is more reliable for heavy compound movements (squat, bench press, deadlift) than for isolation exercises, where local fatigue can limit the number of reps before even reaching the theoretical load.