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's one of the most widely used rep-max estimation formulas, and it's most accurate for sets under about 10 reps — the higher the rep count, the more the estimate drifts from a true max.
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
Most real training programs aren't written as "lift your max" — they're written as percentages of it. Knowing your estimated 1RM lets you calculate exactly what weight a prescribed "75% for 5" or "85% for 2" actually means on the bar.
- Strength blocks — typically 80-95% of 1RM.
- Hypertrophy work — typically 65-80% of 1RM.
- Technique/speed work — typically under 65% of 1RM.
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. It's the standard reference point for programming training percentages.
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's one of the most widely used estimation formulas and works best for rep ranges under about 10.
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.
Strength is one data point
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