What an estimated one-rep max means
A one-repetition maximum (1RM) is the amount of weight a person can lift once with a particular exercise and technique. This page estimates it from a completed set using the Epley equation rather than measuring a true maximum directly.
Formula and example
For a set of more than one repetition, this calculator uses estimated 1RM = load × (1 + reps ÷ 30). For example, lifting 100 kg for 8 completed repetitions gives an estimate of about 127 kg. The formula is an approximation; results can differ with the exercise, range of motion, technique, fatigue, and the person's training experience.
Use it as a planning estimate
The percentages shown below the estimate are arithmetic percentages of the calculated number, not guarantees of how many repetitions someone can safely perform. Do not attempt a maximal lift just to validate a calculator result. Heavy or maximal lifting—especially for young or inexperienced lifters—needs appropriate coaching, equipment, and supervision. Stop if an exercise causes pain and seek qualified guidance when needed.
This calculator accepts completed repetition counts from 1 through 30. Estimates tend to become less reliable as the repetition count rises, because muscular endurance and technique can influence how many repetitions are possible.
Tips for accurate results
Estimates are most reliable when based on a hard set of about 3 to 10 repetitions with good form. Two common formulas are Epley, weight × (1 + reps ÷ 30), and Brzycki, weight × 36 ÷ (37 − reps). For 100 kg for 5 reps, they give about 117 kg and 112.5 kg respectively.
Common mistakes and limits
Accuracy drops as repetitions increase, and the results vary by exercise and by person. Never attempt a true maximum without proper warm-up, safe equipment, and a spotter. Use the estimate for choosing training weights, not as a guarantee of what you can lift on a given day.