Estimated Reps at a Given Load Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/8/2026
The estimated number of reps at a given load is calculated with (1RM ÷ target load − 1) × 30, the Epley formula used in reverse. With a 1RM of 140 kg and a target load of 120 kg, you should be able to perform about 5 reps.
Explanation
Our 1RM calculator answers the question 'what is my one-rep max, based on a number of reps performed at a known load?'. This calculator answers the reverse question, just as useful for programming training: 'based on my already known 1RM, how many reps can I perform at a given load?'. Both calculations rely on the same Epley formula, simply rearranged algebraically to isolate the number of reps rather than the 1RM: reps = (1RM ÷ load − 1) × 30. Like any formula of this type, this estimate remains an approximation built on an average trend: fatigue accumulated during a session, execution technique, and a lifter's experience managing effort close to failure make the actual result vary around this estimate, generally more noticeably beyond about 10-12 theoretical reps, where muscular endurance comes into play more than pure strength. It is a useful tool for programming training as a percentage of 1RM (see also our load from 1RM percentage calculator, which answers the complementary question: what load to choose for a given percentage of my 1RM?) without having to retest an actual maximum, a practice that itself carries an injury risk if done too often.
Example: 1RM of 140 kg, target load of 120 kg
Inputs
Known 1RM: 140 kg. Target load: 120 kg.
Calculation
Estimated reps = (140 ÷ 120 − 1) × 30 = (1.1667 − 1) × 30 ≈ 5.
Result
At 120 kg, you should theoretically be able to perform about 5 reps before muscular failure.
Frequently asked questions
Why is the result theoretical and not guaranteed?
Because the Epley formula, like all 1RM formulas, is built on an average trend observed across a large number of lifters, not on your exact individual profile. Your fatigue on the day, your experience managing effort close to failure, and the exercise performed (formulas are generally more reliable for compound movements like the bench press or squat) make the actual result vary around this estimate.
Does this estimate stay reliable for a high number of reps?
Less and less beyond about a dozen theoretical reps: at a load very light relative to the 1RM, muscular endurance and breathing management become increasingly important compared with pure strength, a factor the Epley formula does not model. It remains most reliable for estimating a number of reps between about 1 and 10.
Is the result the same regardless of the exercise performed?
Not exactly: formulas of this type are generally validated on compound movements (bench press, squat, deadlift), and are less reliable on isolation movements (bicep curl, triceps extension) where local technical fatigue takes over more quickly as reps accumulate.