One Rep Max Calculator
Your one rep max is the most weight you can lift for a single rep on a given movement — the reference point behind every percentage-based strength program. Testing it for real is stressful and risky, so lifters estimate it from submaximal sets: tell the calculator the weight and the reps, and it applies the Epley, Brzycki and Lombardi formulas to give you a working 1RM.
How to estimate your 1RM
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1
Use a recent set
Pick a set you took near failure but not to technical breakdown — ideally 3-6 reps.
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2
Enter weight and reps
Weight in kg or lb, reps as a whole number from 1 to 12.
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3
Read three estimates
Epley, Brzycki and Lombardi tend to agree within 5% in the 3-6 rep range.
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4
Use the average
Programming off the mean of the three is usually safer than trusting any single formula.
The three most-used formulas
| Formula | Equation | Strength with |
|---|---|---|
| Epley | 1RM = w · (1 + r / 30) |
2-10 reps |
| Brzycki | 1RM = w · 36 / (37 − r) |
1-10 reps |
| Lombardi | 1RM = w · r^0.10 |
1-10 reps |
Where w is the weight lifted and r is the number of completed reps.
Percentage of 1RM for common rep ranges
| Reps | Approx %1RM |
|---|---|
| 1 | 100% |
| 2 | 95% |
| 3 | 93% |
| 5 | 87% |
| 8 | 78% |
| 10 | 75% |
| 12 | 70% |
| 15 | 65% |
Which formula to trust
- Brzycki tends to underestimate at very low reps and overestimate past 10.
- Epley is the classic gym-bro formula, slightly aggressive in the 8-12 range.
- Lombardi is conservative and stays more accurate in the 6-15 rep zone.
For powerlifting programming, use Brzycki in the 3-5 rep range. For hypertrophy work, Lombardi off a 6-10 rep set is closer to real 1RM.
Tips for honest numbers
- Don’t pad reps. If the last rep used a grinding 3-second pause at lockout, count it; if form broke, don’t.
- Match the movement. A high-bar back squat 1RM is not the same as a low-bar, and neither is your front-squat 1RM.
- Test periodically, don’t chase daily. True 1RMs vary with sleep, food and stress. Estimates smooth out those swings.
- Always use a spotter or safety bars if you ever test for real. Failed 1RMs on the bench injure shoulders and clavicles.
Frequently Asked Questions
Typically within 5-10% of a real 1RM when based on a set of 3-6 reps taken near failure. Above 10 reps, error grows because rep-max-to-1RM conversion is highly individual at high rep ranges.
Occasionally, if you are competing in powerlifting or strongman, where real singles are the sport. For general strength or hypertrophy training, estimates plus percentage work cover 99% of what you need safely.
They were fit to different populations and rep ranges. Epley came from bodybuilders in the 1980s, Brzycki from strength athletes, Lombardi from military fitness testing. None is universally right.
They were designed around compound lifts — bench, squat, deadlift. They extend reasonably to overhead press and row, but are less useful for isolation work (curls, lateral raises) where strength-endurance skews the relationship.