One Rep Max Calculator
Enter the weight you lifted and how many reps you completed to estimate the heaviest single repetition you could do, using seven established formulas.
Last updated November 2, 2026
Reps completed with good form
Result
Estimated 1RM: about 213.7 lb
| Measure | Value |
|---|---|
| Epley | 215.8 lb |
| Brzycki | 208.1 lb |
| Lander | 210.4 lb |
| Lombardi | 217.3 lb |
| O'Conner | 208.1 lb |
| Mayhew | 220.2 lb |
| Wathan | 215.7 lb |
| Average of the seven | 213.7 lb |
| Percent of 1RM | Weight |
|---|---|
| 95% | 203 lb |
| 90% | 192.3 lb |
| 85% | 181.6 lb |
| 80% | 170.9 lb |
| 75% | 160.2 lb |
| 70% | 149.6 lb |
| 65% | 138.9 lb |
| 60% | 128.2 lb |
| 55% | 117.5 lb |
| 50% | 106.8 lb |
Estimates are most accurate for 10 or fewer reps and differ from your true max. Testing a real max carries injury risk, so use a spotter and ask a coach if you are unsure. General estimate only, not medical advice. Talk to a qualified health professional about your own situation.
Show the work
Formula: Seven published formulas are applied to the weight and reps, then averaged.
- You entered 185 lb for 5 reps.
- Epley: 185 × (1 + 5 / 30) = 215.8 lb.
- Brzycki: 185 × 36 / (37 − 5) = 208.1 lb.
- Lander: 100 × 185 / (101.3 − 2.67123 × 5) = 210.4 lb.
- Lombardi: 185 × 5^0.1 = 217.3 lb.
- O'Conner: 185 × (1 + 0.025 × 5) = 208.1 lb.
- Mayhew: 100 × 185 / (52.2 + 41.9 × e^(−0.055 × 5)) = 220.2 lb.
- Wathan: 100 × 185 / (48.8 + 53.8 × e^(−0.075 × 5)) = 215.7 lb.
- Average of the seven = 213.7 lb.
Result: Estimated 1RM: about 213.7 lb
How one rep max is estimated
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Each formula predicts a one-rep max from a set of several reps. Epley multiplies the weight by 1 + reps ÷ 30. Brzycki uses 36 ÷ (37 − reps). Lander, Lombardi, O’Conner, Mayhew and Wathan use their own curves. The calculator shows all seven and their average, because they disagree slightly.
For 185 lb × 5 reps the formulas give about 208 to 220 lb with an average of 213.7 lb. They are most accurate for sets of 10 or fewer reps and are limited to 12 reps here. The percentage table turns the average into training weights.
See how we calculate for the formulas, sources and review schedule behind every calculator.
This is an estimate, not medical advice
Estimates from submaximal sets are rough and are not a substitute for coaching. Lifting heavy carries a risk of injury: use good form, a spotter or safety bars, and ask a qualified coach or doctor if you are unsure. This page has not been reviewed by a medical professional.
Sources
Official and primary sources for the statements on this page. Their authors have not reviewed or endorsed this page.
- LeSuer DA, McCormick JH, Mayhew JL, et al. 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. Compared seven repetitions-to-fatigue equations in 67 untrained students: predictions correlated highly with the true 1-RM, but most differed significantly from it and all underestimated the deadlift, so results here are estimates
- Abdul-Hameed U, Rangra P, Shareef MY, Hussain ME. Reliability of 1-repetition maximum estimation for upper and lower body muscular strength measurement in untrained middle aged type 2 diabetic patients. Asian J Sports Med 2012. Writes the Brzycki equation as 1RM = W ÷ [102.78 − 2.78 R] × 100, which equals weight ÷ (1.0278 − 0.0278 × reps). This page uses the equivalent form weight × 36 ÷ (37 − reps), which differs only by rounding of the constants (under 0.05%)
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance 1993;64(1):88-90. Original publication of the Brzycki equation, cited as the reference by the article above. We could not read the paper itself
Only the Brzycki form is confirmed against a published article. We did not locate or verify the original publications for the Epley, Lander, Lombardi, O’Conner, Mayhew and Wathan equations, so they are not cited and their coefficients are unverified. We did not confirm that the seven equations in the LeSuer study are the same seven used here. Estimates are least reliable above about 10 repetitions.
How to use the One Rep Max Calculator
- Choose pounds or kilograms.
- Enter the weight you lifted and the reps you completed with good form.
- Read the estimates, the average and the percentage chart, then use Copy, Print or Share.
Worked example
Lifting 185 lb for 5 reps: Epley gives 185 × (1 + 5 ÷ 30) = 215.8 lb and Brzycki gives 185 × 36 ÷ 32 = 208.1 lb. The average of the seven formulas is 213.7 lb.
| Percent of 1RM | Weight |
|---|---|
| 95% | 203.0 lb |
| 90% | 192.3 lb |
| 85% | 181.6 lb |
| 80% | 171.0 lb |
| 75% | 160.3 lb |
| 70% | 149.6 lb |
Frequently asked questions
What is a one-rep max?
The heaviest weight you can lift for one repetition with good form.
Which 1RM formula is most accurate?
None is best for everyone. Accuracy depends on the exercise and your fitness, so the average of several is a reasonable guide.
Why are only 1 to 12 reps allowed?
Estimates get unreliable for high-rep sets, and some formulas break down.
Is it safe to test my true max?
It carries injury risk. Use a spotter or safety equipment and ask a coach, or use the estimate instead.
Are my numbers stored or sent anywhere?
No. The calculation runs in your browser and nothing you enter is saved or uploaded.