Free tool
One rep max calculator
Enter the weight and reps from a real set to estimate your 1RM — plus a full percentage table so you can actually program with it.
How this is calculated
This uses the Epley formula: 1RM = weight × (1 + reps ÷ 30). It is a commonly used estimate, not a direct test. The relationship between reps and maximum load varies by lift and person, so treat the result as approximate, especially at higher rep counts.
This is an estimate, not a guarantee. Bar speed, fatigue, technique, and how close the set was to failure all move the real number. Use it for programming percentages, not as a substitute for how a lift actually feels that day.
Why the percentage table matters
Some training programs prescribe loads as a percentage of a tested or estimated 1RM. The examples below are broad conventions, not universal definitions of strength, hypertrophy or technique work; the right load depends on the program, lift and lifter.
- Heavier work — a program may use loads around 80-95% of estimated 1RM.
- Moderate-load work — programs may use a wider range, including loads around 65-80%.
- Technique or speed practice — may use lighter loads, when that suits the program.
Questions
What is a one rep max (1RM)?
Your one rep max is the heaviest weight you can lift for a single complete rep with good form. Programs may use it as a reference for training loads, often through an estimated 1RM.
How accurate are 1RM calculators?
Estimation formulas like Epley get less accurate the higher the rep count used to estimate from — a set of 3-5 reps gives a much more reliable estimate than a set of 15-20. Fatigue, bar speed, and technique on the day all move the real number too.
What formula does this calculator use?
The Epley formula: weight × (1 + reps ÷ 30). It estimates a maximum from a submaximal set; accuracy varies by lift, person and number of repetitions.
Should I actually test my 1RM?
Not usually necessary for general training — a true 1RM test carries injury risk and most programming works fine off an estimate. It's more relevant if you compete in a strength sport that tests it directly.
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