1 Rep Max Calculator
Estimate your one-rep max (1RM) from a submaximal set. Enter the weight and reps, then choose a formula.
What Is a 1 Rep Max?
Your 1 rep max (1RM) is the maximum amount of weight you can lift for a single repetition with good form. Since true max attempts can be fatiguing and risky, most people use a 1 rep max calculator formula based on a lighter set (for example, 225 x 5 on bench press) to estimate their max.
Common 1RM Formulas
Different formulas were developed from different populations and exercises, so estimates can vary slightly. That is normal.
| Formula | Expression | Typical Use |
|---|---|---|
| Epley | 1RM = weight × (1 + reps/30) | Popular all-purpose estimate |
| Brzycki | 1RM = weight × 36 / (37 − reps) | Common for lower rep ranges |
| Lombardi | 1RM = weight × reps0.10 | Slightly higher estimates at some rep counts |
| O'Conner | 1RM = weight × (1 + reps/40) | Conservative and simple |
| Mayhew et al. | 1RM = (100 × weight) / (52.2 + 41.9 × e-0.055×reps) | Research-based prediction model |
Which Formula Should You Use?
- If you want a balanced estimate, use Average of All Formulas.
- If your coach or program specifies one method, use that method consistently.
- For powerlifting tracking, consistency matters more than chasing the highest estimate.
How to Use Your Estimated 1RM for Training
Once you have an estimated max, you can build working sets as a percentage of that value:
- 60–70%: technique work, speed, warm-up volume
- 70–80%: hypertrophy and base strength
- 80–90%: heavier strength work
- 90%+: peaking and low-rep intensity
The calculator above automatically gives a percentage chart to make this easy for bench press, squat, deadlift, and overhead press.
Example Calculation
If you lift 225 lb for 5 reps, your estimated 1RM usually lands around the mid-250s to high-260s depending on formula. That spread is expected. Use the same exercise setup, same range of motion, and same formula each week to track progress reliably.
Accuracy Tips
1) Stay in a practical rep range
Predictions are strongest in low-to-moderate reps (about 2–10). Very high reps can under- or over-estimate true max strength.
2) Keep technique consistent
Touch-and-go bench, pause bench, high-bar squat, and low-bar squat can all produce different numbers. Compare like with like.
3) Use RPE and fatigue context
A set performed close to failure gives a better estimate than a set stopped far from failure. Sleep, stress, and nutrition also matter.
Safety Note
A calculator is an estimate—not a command to max out today. Increase loads gradually, use spotters when appropriate, and prioritize form. If you have injury concerns, consult a qualified coach or medical professional.