Your one-rep max is the most weight you can lift for a single repetition. This calculator estimates it from a lighter set using the Epley formula, so you can program training loads without a risky max attempt.
Sample input: Weight lifted (per set): 100, Repetitions completed: 5
Estimated 1RM: 116.7 (Epley formula)
Lifting 100 for 5 reps estimates a one-rep max of about 116.7. Useful training loads: 90% = 105, 80% = 93.4, 70% = 81.7.
A one-rep max (1RM) is the heaviest weight you can lift for one full repetition of an exercise. It is the standard reference for setting strength-training loads.
It uses the Epley formula (1985): 1RM equals weight times (1 plus reps divided by 30). It is one of the most widely used and validated 1RM estimators.
Estimates are most accurate at 10 reps or fewer, typically within a few percent of a tested max. Above 10 reps fatigue and technique reduce accuracy, so use lower-rep sets for the best estimate.
Strength programs prescribe loads as a percentage of 1RM, for example 80 percent for strength work or 70 percent for hypertrophy. The tool shows common training percentages for your estimate.