One rep max
1RM Calculator
Estimate your one rep max from a submaximal set. Enter the weight you lifted and how many reps you got, and the calculator does the rest.
By Tyler Talaga, RN · Updated
How do you calculate a one rep max?
Take a set of 2 to 10 reps close to failure, then put the weight and the rep count into a prediction formula. Each formula assumes a fixed relationship between how many reps you can do and how close the weight is to your max. The three most common:
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Lombardi: 1RM = weight × reps^0.10
For 225 lb × 5 reps, they give:
| Formula | Estimated 1RM |
|---|---|
| Epley | 263 lb |
| Brzycki | 253 lb |
| Lombardi | 264 lb |
The spread of about 10 lb is normal. Pick one formula and stick with it, so your estimates stay comparable from cycle to cycle.
How accurate is a 1RM calculator?
Accurate enough to program from, and most accurate when the set is short. Studies comparing these equations find they hold up best for sets of about 10 reps or fewer, and that accuracy varies by lift. Past 10 reps, muscular endurance starts to matter as much as strength, and the formulas drift apart.
Fewer reps, closer to failure, give the best estimate. A set of 3 to 5 is the sweet spot for most lifters.
What percentage of your 1RM can you lift for reps?
The Epley formula, turned around, gives this rough guide:
| Reps to failure | % of 1RM |
|---|---|
| 1 | 100% |
| 2 | 94% |
| 3 | 91% |
| 4 | 88% |
| 5 | 86% |
| 6 | 83% |
| 7 | 81% |
| 8 | 79% |
| 9 | 77% |
| 10 | 75% |
| 12 | 71% |
Should you test a true 1RM?
Most lifters don't need to. An estimated max is enough to set training percentages, and it doesn't carry the risk of a true max attempt.
Clinically, that risk is real for some people. Heavy lifts done while holding your breath can push blood pressure far above resting levels for a few seconds. If you have high blood pressure, heart disease, a history of aneurysm or stroke, or eye conditions such as retinopathy, estimate your max instead of testing it, and talk to your physician before training near it.
Sources
- Epley B. Poundage Chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985.
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance. 1993;64(1):88–90.
- Lombardi VP. Beginning Weight Training. Dubuque, IA: W.C. Brown; 1989.
- LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res. 1997;11(4):211–213.
- MacDougall JD, Tuxen D, Sale DG, Moroz JR, Sutton JR. Arterial blood pressure response to heavy resistance exercise. J Appl Physiol. 1985;58(3):785–790.