Lifting 80 kg for 6 reps on the bench press gives an estimated one-rep max of about 95 kg. The Epley formula is 1RM = weight × (1 + reps ÷ 30), and the calculator averages it with five other published formulas.
How do you estimate a one-rep max?
Your one-rep max (1RM) is the heaviest weight you can lift once with good form. Testing it is tiring and risky, so most lifters estimate it from a harder set of 3 to 8 reps. Several equations do this by assuming that the more reps you can do with a weight, the lighter it is compared with your max. This calculator runs six: Epley (weight × (1 + reps/30)), Brzycki (weight × 36 ÷ (37 − reps)), Lander, Lombardi, O’Conner and Mayhew, then averages them.
Which formula is best?
None is perfect, and they agree closely below 10 reps and drift apart above that. Brzycki and Epley are the most used. For 5 reps at 100 kg the six formulas give between 112 and 119 kg, a spread of about 6%. Using the average reduces the bias of any single one. If you only lift for fewer than 5 reps, any of them is fine.
Using the percentage table
| Goal | % of 1RM | Typical reps |
|---|---|---|
| Maximal strength | 85% to 95% | 1 to 5 |
| Strength and size | 70% to 85% | 5 to 10 |
| Hypertrophy, volume | 60% to 75% | 8 to 15 |
| Endurance | 50% to 60% | 15 to 30 |
Programmes such as 5×5 or 5/3/1 prescribe loads as a percentage of 1RM. Be conservative: use a training max of about 90% of your estimate, and update it every few weeks. Rep estimates are not exact. Fatigue, sleep and technique change how many reps you really get at a percentage.
Bodyweight and relative strength
A bench press of 1.0 times bodyweight is a common beginner milestone, 1.5 times is intermediate for men and 2.0 times is advanced. Track your strength next to muscle mass with the FFMI calculator, and make sure you eat enough protein for recovery, using the Protein Calculator.
The calculation works for squats, deadlifts, overhead press and rows as well, although estimates for deadlifts are less reliable because grip often limits the set.
How to use this calculator
- Enter the weight in kilograms and the number of clean reps you completed.
- Read the average estimate and the result from each formula.
- Use the percentage table to plan sets and rep ranges.
- Retest with a heavier set rather than a true max if you can’t train with a spotter.
Key figures at a glance
| Epley | weight × (1 + reps ÷ 30) |
|---|---|
| Brzycki | weight × 36 ÷ (37 − reps) |
| Most accurate range | 2 to 10 reps |
Frequently asked questions
Lift a weight to near failure for 3 to 8 reps and apply a formula such as Epley: weight × (1 + reps ÷ 30).
Within about 5% for sets of up to 10 reps, if the set was taken close to failure with good form.
Roughly 75%.
Only with a spotter and after a warm-up. Many lifters prefer estimates to avoid injury.
Yes, although accuracy drops for lifts where grip or form breaks down early.