What is a one rep max?
Your one rep max (1RM) is the heaviest weight you can lift for a single full repetition of an exercise with good form. It is the standard measure of maximal strength, and it differs from lift to lift, so a bench press max says little about your squat or deadlift.
Testing a true 1RM means working up to an all-out lift, which is tiring and riskier without experience or a spotter. This one rep max calculator (also called a 1 rep max calculator) estimates it instead from a set you can already do: enter the weight and how many reps you completed, and it predicts your 1RM along with the weight you could handle at other rep counts.
How to calculate one rep max: the 1RM formulas
The 1RM calculator offers three widely used formulas, where w is the weight lifted and r is the number of reps:
- Epley: 1RM = w × (1 + r ÷ 30). With a single rep, the weight itself is your 1RM.
- Brzycki: 1RM = w × 36 ÷ (37 − r)
- Lombardi: 1RM = w × r0.1
For example, 185 lb for 5 reps gives an estimated one rep max of 215.8 lb with Epley, 208.1 lb with Brzycki, and 217.3 lb with Lombardi. The formulas agree closely at low reps and drift apart as reps rise, which is why the calculator accepts 1 to 10 reps.
The same formula, run in reverse, fills in the tables: the weight you could lift for a given number of reps, and the most reps you could do at a given percentage of your 1RM.
Bench, squat, and deadlift max calculator
The formulas work for any barbell or machine lift, so you can use this page as a bench press calculator or bench max calculator, a squat max calculator, or a deadlift max calculator. Enter a set from the lift you want to estimate and keep a separate 1RM for each exercise.
Treat a deadlift estimate as a floor rather than a ceiling. In a study of seven prediction equations, every one underestimated the deadlift 1RM, even though their predictions correlated strongly with tested maxes.
Using your 1RM to plan training
Programs often prescribe loads as a percentage of 1RM. The ranges below are a common general guide, not a strict rule:
| Goal | % of 1RM | Reps | Sets |
|---|---|---|---|
| Power | 50% to 60% | 3 to 5 | 4 to 6 |
| Muscular endurance | About 70% | 10 to 15 | 4 to 6 |
| Muscle growth (hypertrophy) | 70% to 80% | 7 to 12 | 3 to 5 |
| Maximal strength | 80% to 100% | 1 to 3 | 3 to 4 |
The "Max reps" column in the results is how many reps you could do at that load before failing, not how many you should do. Leave a rep or two in reserve on most working sets.
Frequently asked questions
How accurate is a 1RM calculator?
An estimate from a hard set of a few reps taken close to failure is usually close to a tested max. Accuracy falls as reps rise, and it also varies by lift, so treat the result as a starting point and adjust it to how your sets actually feel.
Which one rep max formula is best?
No single formula wins for every lifter or lift. Epley and Brzycki are the most common and give exactly the same answer at 10 reps, while Lombardi predicts slightly higher at low reps and lower at high reps. Pick one and stick with it so your progress is comparable over time.
Why is the limit 10 reps?
A long set depends more on muscular endurance than on maximal strength, so estimates from it are less reliable. Research on multiple-rep testing recommends using no more than 10 reps to estimate a one rep max.
Should I test my real one rep max?
Experienced lifters sometimes do, with a proper warm-up and a spotter. For most people, an estimate from a hard set of 3 to 5 reps is safer and accurate enough to set training loads.
Things to keep in mind
The results are estimates. Fatigue, technique, sleep, and the equipment you use all change how much you can lift on a given day. Stop if you feel pain, and talk to a doctor before heavy lifting if you have a health condition or injury.
What's changed
- Launched.
References
- LeSuer et al. (1997), The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift
tests how accurately 7 equations predict 1RM from reps to fatigue in the bench press, squat, and deadlift
- Reynolds et al. (2006), Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry
supports using no more than 10 reps for linear 1RM estimates in the bench press and leg press