Home / Health / One Rep Max Calculator
One Rep Max (1RM) Calculator
Enter the weight you lifted and how many clean repetitions you completed to estimate the heaviest single you could lift, using three published formulas and an average, with a table of training percentages.
The three formulas
A one rep max (1RM) is the heaviest load you can lift for one correctly performed repetition. Testing it directly is tiring and carries injury risk for beginners, so coaches estimate it from a lighter set taken close to failure. Each formula turns the weight w and the repetitions r into a predicted single:
- Epley:
w × (1 + r ÷ 30) - Brzycki:
w × 36 ÷ (37 − r) - Lander:
100 × w ÷ (101.3 − 2.67123 × r)
For 100 kg lifted five times these give 116.7, 112.5 and 113.7 kg, so the average is about 114.3 kg. The formulas agree closely at low reps and drift apart as reps rise, which is why the calculator shows all three rather than hiding the spread.
Using the percentage table
Strength programmes are often written as a percentage of 1RM, for example "four sets of five at 80%". The table converts your estimated maximum into those loads. Round to the nearest plate you own; a difference of a kilogram or two matters less than clean technique. The relationship between percentage and repetitions varies between lifts and between people, so use the table as a starting point and adjust by how the sets feel.
Lower-body compound lifts tend to allow more repetitions at a given percentage than small isolation exercises, and trained lifters may differ from beginners. Take the percentages as a convenient scale, not a promise of how many reps you can complete.
Getting a trustworthy estimate
- Use a hard set. The set should end near failure, with perhaps one rep left in reserve. A comfortable set of five understates your max.
- Keep reps low. Between 2 and 6 gives the best predictions. Past 10 the equations extrapolate too far and endurance matters as much as strength.
- Count only strict reps. Bouncing the bar, partial range or lifting with a spotter pulling should not count.
- Compare like with like. Use the same lift, equipment and warm-up each time you track progress.
Safety and limits
An estimate is only a number. Do not attempt a true maximum without a warm-up, correct technique, safety bars or a spotter, and a fit-for-purpose lift such as squat or bench in a rack. People who are new to training, who are returning from injury, who have heart or blood pressure conditions, or who are pregnant should take advice from a qualified coach or clinician before lifting near maximal loads. This calculator is educational and not medical advice. It also does not account for fatigue, tempo, sleep or the day-to-day variation that moves a real max by several percent.
Worked example
A lifter completes 5 clean reps with 100 kg on the bench press.
Inputs
| Weight lifted | 100 |
|---|---|
| Repetitions completed | 5 |
| Weight unit | kg |
Result
Average of three formulas from 100.0 kg for 5 reps.
| Epley | 116.7 kg |
|---|---|
| Brzycki | 112.5 kg |
| Lander | 113.7 kg |
| Average of the three | 114.3 kg |
Training weights as a percentage of the average 1RM
| Percent of 1RM | Weight (kg) |
|---|---|
| 100% | 114.3 |
| 95% | 108.6 |
| 90% | 102.9 |
| 85% | 97.1 |
| 80% | 91.4 |
| 75% | 85.7 |
| 70% | 80.0 |
| 65% | 74.3 |
| 60% | 68.6 |
| 55% | 62.9 |
| 50% | 57.1 |
- Epley: weight × (1 + reps ÷ 30). Brzycki: weight × 36 ÷ (37 − reps). Lander: 100 × weight ÷ (101.3 − 2.67123 × reps).
Medical disclaimer: This tool is for education and general planning. It is not medical advice and does not diagnose any condition. If you are pregnant, under 18, have an eating-disorder history or a medical condition, speak to a doctor or registered dietitian before changing your diet or exercise.
Frequently asked questions
What is a one rep max?
It is the heaviest weight you can lift for a single repetition with correct form on a given exercise. It is specific to the lift, so your squat, bench press and deadlift each have their own.
Which 1RM formula is most accurate?
None is best for everyone. Epley, Brzycki and Lander agree closely for sets of about two to six reps. Averaging the three, as this page does, reduces the chance that one formula over- or under-shoots.
How many reps should I use for the estimate?
Use a hard set of between two and six reps if possible. Estimates from sets above ten reps are much less reliable because endurance rather than maximal strength limits the set.
Is it safe to test a true one rep max?
It can be done safely by trained lifters with a spotter or safety bars and a proper warm-up. Beginners and people with medical conditions are usually better off using an estimate from a lighter set.
Can I use pounds instead of kilograms?
Yes. The formulas are unit-free, so any unit gives a result in the same unit. Choose pounds in the unit menu to label the answers and the table correctly.
Related calculators
References and sources
- Epley B. (1985). Poundage Chart. Boyd Epley Workout, University of Nebraska.
- 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.
- LeSuer DA, et al. (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 (includes the Lander equation).
- National Strength and Conditioning Association, resistance training guidance. Link