One-Rep Max Calculator
Estimate your 1RM from any working set, with a training percentage table.
| % of 1RM | Weight |
|---|
Estimate your one-rep max (1RM) from a set of reps using the Epley formula, with a ready-made table of common training percentages of that max.
Examples
| Set | Estimated 1RM |
|---|---|
| 225 lb × 3 reps | 248 lb |
| 185 lb × 5 reps | 216 lb |
| 135 lb × 8 reps | 171 lb |
| 100 lb × 10 reps | 133 lb |
The math works the same in kilograms — switch the unit and the table follows.
Training percentages and typical reps
| % of 1RM | Rough reps possible | Typical goal |
|---|---|---|
| 90–95% | 2–4 | Maximum strength |
| 80–85% | 5–8 | Strength |
| 70–75% | 8–12 | Muscle growth |
| 60–65% | 12–15+ | Endurance, warm-up sets |
These ranges are general guides; the number of reps you can do at a given percentage varies between people and between lifts.
Why estimate instead of testing a true max?
Lifting a true one-rep max is tiring and carries a higher risk of injury, especially without a spotter or experience. Estimating from a set of 3–10 reps gives a number that's close enough to plan your training, and you can recheck it every few weeks as you get stronger. Use a weight you can lift with good form, and stop the set when your form starts to break down.
Frequently asked questions
What formula does this use?
The Epley formula: 1RM = weight × (1 + reps ÷ 30) — one of the most widely used estimates for a single-rep maximum from a higher-rep set.
How accurate is an estimated 1RM?
It's a solid estimate for sets of up to about 10 reps; beyond that, formulas get less reliable since very high-rep sets are more about muscular endurance than pure strength.
What are the percentage columns for?
Many strength programs prescribe working weights as a percentage of your 1RM (e.g. "work up to 80% for 5 reps") — the table converts your estimated max into those common training percentages.
How many reps should I use for the most accurate estimate?
Sets of about 3 to 6 reps give the closest estimates. The further you get past 10 reps, the more the result reflects endurance rather than maximum strength.
Is it safe to test my real one-rep max?
It can be for experienced lifters with good technique and a spotter or safety bars. Beginners are usually better off using an estimate like this one. If you have an injury or health condition, check with a doctor or qualified coach first.