What is a one rep max (1RM)?
A one rep max (1RM) is the maximum weight you can lift for a single repetition of an exercise with good form. It's the gold-standard measure of absolute strength in powerlifting and strength training.
Epley Formula 1RM Calculator
Developed by Boyd Epley in 1985, one of the most widely cited 1RM equations in strength research.
w × (1 + r/30) — Developed by Boyd Epley in 1985, one of the most widely cited 1RM equations in strength research.
Use the Epley Formula 1RM Calculator
This page is tuned for lifters who want a fast Epley formula 1RM calculation from a normal working set, then compare that result against the other major equations.
- Best for: moderate rep sets when you want a widely cited estimate that most lifters already recognize
- Rep range: usually strongest from about 3-10 reps before fatigue distorts the estimate
- Worked example: 225 lb x 5 reps estimates about 262 lb with the Epley equation.
5 reps
One Rep Max
5 reps @ 225lb
263
lb
Epley formula
Big Four Strength Standards
Strength levels for a 200lb male, age 30 lifting 263lb in each lift type · enter your details.
Rep Max Projections
Epley algorithm
| Reps | Weight (lb) |
|---|---|
| 1RM | 263lb |
| 2RM | 247lb |
| 3RM | 239lb |
| 4RM | 232lb |
| 5RM(current) | 225lb |
| 6RM | 219lb |
| 7RM | 213lb |
| 8RM | 208lb |
| 9RM | 202lb |
| 10RM | 197lb |
| 20RM | 158lb |
Percentage Calculator
Based on 263lb estimated max
| Intensity | Weight (lb) |
|---|---|
| 100% | 263lb |
| 95% | 250lb |
| 90% | 237lb |
| 85% | 224lb |
| 80% | 210lb |
| 75% | 197lb |
| 70% | 184lb |
| 65% | 171lb |
| 60% | 158lb |
| 55% | 145lb |
| 50% | 132lb |
One Rep Max Calculator FAQ
Which 1RM formula is most accurate?
No single formula is universally most accurate — accuracy depends on the individual and rep range. Brzycki is considered most reliable for lower rep ranges (1–6 reps). Epley is widely cited in research. This calculator shows all 7 formulas side by side so you can see the full range of estimates.
How many reps should I use to estimate my 1RM?
Sets of 3–10 reps give the most reliable 1RM estimates. Below 3 reps you're already near your max. Above 10 reps, fatigue factors make estimates less accurate. A set of 5 reps is a common sweet spot.
What is an E1RM (estimated one rep max)?
An E1RM is a calculated estimate of your one rep max based on a submaximal set — for example, the weight you lifted for 5 reps. E1RM formulas let you track strength progress without the risk of actual max testing every session.
Can I use this calculator for squat, bench press, and deadlift?
Yes. This 1RM calculator works for any barbell lift — back squat, bench press, deadlift, strict press, and more. Enter your working weight and rep count and the calculator estimates your max across all 7 formulas.
