# What is my one rep max?

Estimates the one-repetition maximum (1RM) from a weight lifted for 1 to 10 reps with the Brzycki and Epley equations, or the weight to use for a number of reps.

- Page: https://www.acalculator.org/sports/one-rep-max-calculator
- JSON spec: https://www.acalculator.org/sports/one-rep-max-calculator.json
- Version: d18e4edbd734

## Default answer

Example with the default inputs (Weight lifted 200 lb, Reps 5): Lifting 200 lb for 5 reps puts your estimated one rep max at 225 lb.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| w | Weight lifted | The weight you lifted for the set, including the bar. |
| r | Reps | How many full repetitions you did with that weight before you could not do another. |
| max | One rep max (Brzycki) | The most you could lift once, estimated with Brzycki’s equation. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| weight | Weight lifted | The weight you lifted for the set, including the bar. |
| reps | Reps | How many full repetitions you did with that weight before you could not do another. |
| oneRm | One rep max (Brzycki) | The most you could lift once, estimated with Brzycki’s equation. |
| epley | One rep max (Epley) | The one rep max from Epley’s equation: weight × (1 + reps ÷ 30). |
| average | Average of both | The mean of the Brzycki and Epley estimates. |

## Method

1RM = weight × 36 ÷ (37 − reps) (Brzycki 1993); Epley (1985): 1RM = weight × (1 + reps ÷ 30).

## Assumptions

- The set went to failure: you could not have done one more rep with good form.
- Reps are from 1 to 10. Both equations lose accuracy with more reps, and they were fit on lifts such as the bench press, squat and deadlift.
- Brzycki gives exactly the weight lifted for 1 rep. Epley gives 1/30 more than the weight for 1 rep; that is how the equation is written.
- The weight lifted and the one rep max are at most 2,000 lb (907 kg).

## Worked examples

1. w = 90.718474, r = 5 gives max = 102.058283, epley = 105.83822, average = 103.948251. Source: hand calculation in content.mdx: Brzycki (1993) 200 × 36 ÷ 32 = 225 lb = 102.06 kg; Epley (1985) 200 × (1 + 5 ÷ 30) = 233.3 lb = 105.84 kg; mean 229.2 lb.
2. w = 100, r = 10 gives max = 133.333333, epley = 133.333333. Source: hand calculation in content.mdx: 100 × 36 ÷ 27 = 133.33 kg; 100 × (1 + 10 ÷ 30) = 133.33 kg.
3. max = 100, r = 8 gives w = 80.555556. Source: hand calculation in content.mdx: weight = 100 × (37 − 8) ÷ 36 = 80.56 kg.
4. w = 135, max = 150 gives r = 4.6. Source: hand calculation in content.mdx: reps = 37 − 36 × 135 ÷ 150 = 4.6.

## FAQ

### How do I calculate my one rep max?

Lift a weight for as many good reps as you can (up to 10), then use a formula. Brzycki: 1RM = weight × 36 ÷ (37 − reps). Epley: 1RM = weight × (1 + reps ÷ 30). For 200 lb × 5 reps, Brzycki gives 225 lb and Epley 233 lb.

### Which one rep max formula is most accurate?

No single formula is best for every lift and person. In a study of 67 untrained college students (LeSuer and others, 1997), seven equations all tracked the real 1RM closely (r above 0.95), but most had a small average bias, and all of them underestimated the deadlift. Brzycki and Epley agree exactly at 10 reps and differ most at about 3 to 5 reps.

### Why use 10 reps or fewer?

Both formulas were built from sets of low to moderate reps. With more reps, endurance matters more than strength, and the estimate becomes less reliable. Brzycki recommended no more than 10 reps.

### What weight should I use for a set of 8?

Enter your one rep max and 8 reps, and leave the weight empty. With Brzycki, weight = 1RM × (37 − reps) ÷ 36, so a 100 kg max suggests about 80.6 kg for 8 reps.

### Is it safe to test a real one rep max?

A true max attempt is heavy and needs a warm-up, good technique and a spotter or safety bars. Estimating from a set of 3 to 10 reps is a common, lower-risk alternative.

## Sources

- Brzycki, M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation and Dance 64(1), 88–90. https://doi.org/10.1080/07303084.1993.10606684
- Epley, B. (1985). Poundage chart. In Boyd Epley Workout. Lincoln, NE: Body Enterprises.
- LeSuer, D. A., J. H. McCormick, J. L. Mayhew, R. L. Wasserstein, and M. D. Arnold (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research 11(4), 211–213.
- NIST Special Publication 811 (2008), Appendix B.8: 1 lb = 0.45359237 kg exactly. https://www.nist.gov/pml/special-publication-811