One Rep Max Calculator
Enter the weight you lifted and how many reps you completed to estimate your one rep max with six common formulas, then use the percentage table to set training loads.
Result
- Epley
- 116.7 kg
- Brzycki
- 112.5 kg
- Lander
- 113.7 kg
- Lombardi
- 117.5 kg
- O'Conner
- 112.5 kg
- Wathan
- 116.6 kg
| % of 1RM | Weight | Typical reps |
|---|---|---|
| 100% | 114.9 kg | 1 |
| 95% | 109.2 kg | 2 |
| 90% | 103.4 kg | 4 |
| 85% | 97.7 kg | 6 |
| 80% | 91.9 kg | 8 |
| 75% | 86.2 kg | 10 |
| 70% | 80.4 kg | 12 |
| 65% | 74.7 kg | 15 |
| 60% | 68.9 kg | 18 |
| 55% | 63.2 kg | 20 |
| 50% | 57.5 kg | 25 |
What is a one rep max?
Your one rep max (1RM) is the heaviest weight you can lift once with good form in a given exercise. It is the standard measure of maximal strength in powerlifting and the reference point for most strength programs, which prescribe sets as a percentage of 1RM, for example "5 reps at 80%". Knowing your 1RM therefore lets you follow a program accurately and track progress over months without guessing.
Why estimate instead of testing?
An actual max attempt is tiring, needs a spotter or safety bars, and carries the highest injury risk of any set you will do. Form also breaks down under a true maximum, so the number you get is partly a measure of nerve. Estimating from a submaximal set of 3 to 10 reps avoids all of that and, within that rep range, is accurate to within a few percent for most lifters. It also lets you update the estimate from any hard training set.
The formulas and a worked example
Every formula takes the weight lifted (w) and the reps completed (r). For a single rep they all return the weight itself. With the default set of 100 kg for 5 reps:
| Formula | Equation | 100 kg × 5 |
|---|---|---|
| Epley | w × (1 + r ÷ 30) | 100 × (1 + 5 ÷ 30) = 116.7 kg |
| Brzycki | w × 36 ÷ (37 − r) | 100 × 36 ÷ 32 = 112.5 kg |
| Lander | 100w ÷ (101.3 − 2.67123r) | 10,000 ÷ 87.94 = 113.7 kg |
| Lombardi | w × r0.10 | 100 × 50.1 = 117.5 kg |
| O'Conner | w × (1 + 0.025r) | 100 × 1.125 = 112.5 kg |
| Wathan | 100w ÷ (48.8 + 53.8e−0.075r) | 10,000 ÷ 85.78 = 116.6 kg |
The six estimates range from 112.5 to 117.5 kg and average 114.9 kg, which is the headline figure. Epley and Brzycki are the two you will see most often; they agree exactly at 10 reps (both give 1.333 × w) and diverge either side of it, Brzycki being lower for fewer reps and higher for more.
How to use this calculator
- Pick kilograms or pounds. The unit is only a label; the maths is the same.
- Enter the weight of a recent set taken close to failure and the number of clean reps you completed. Sets of 3 to 10 reps give the best estimate.
- Read the average 1RM and the individual formulas. If your program names a formula, use that row.
- Use the percentage table to pick loads: for example, 5 sets of 5 at 80% of a 115 kg max is 92 kg.
Using training percentages
The table shows the load at each percentage of your estimated max and the number of reps most lifters can manage there. Strength work typically lives at 80 to 95% for 1 to 6 reps, hypertrophy work at 65 to 80% for 6 to 15 reps, and warm-ups and technique practice below 65%. The reps column is a population average: well trained lifters and people with a lot of fast-twitch fibre get fewer reps at a given percentage, endurance athletes get more, so note what you actually achieve and adjust.
Safety and limitations
- Technique first. Only count reps performed with full range of motion and good form; partial or assisted reps inflate the estimate.
- Do not jump straight to the estimate. Work up over several sessions before attempting anything above 90%, and always use a spotter or safety bars on squats and bench press.
- Estimates drift above 10 reps. The formulas were fitted on low-rep sets; a 20-rep set tells you more about endurance than strength.
- Exercises differ. The formulas were developed mainly on the bench press. Expect slightly different rep-to-percentage relationships on squats, deadlifts and isolation exercises.
- Day-to-day variation from sleep, nutrition and fatigue can move your real max by 5% either way. Pair strength goals with the macro calculator and the lean body mass calculator to make sure training is supported by recovery.
These figures are estimates for planning training and are not medical advice.
Frequently asked questions
Which one rep max formula is the most accurate?
For sets of 10 reps or fewer, the formulas agree within a few percent and any of them is fine; Epley and Brzycki are the most widely used. Brzycki tends to be more accurate for low-rep sets, while Epley and Wathan hold up better as reps rise. Averaging them, as the headline figure does, smooths out the differences.
Why should I enter 10 reps or fewer?
All the formulas were fitted to sets in the 1 to 10 rep range. Above that, muscular endurance matters more than maximal strength, and the estimates drift apart quickly. A set of 20 reps can over- or under-estimate your true max by 10% or more.
Does the same estimate work for squats, deadlifts and bench press?
Roughly, but the formulas were developed mainly on the bench press. Lifters often get a few more reps at a given percentage on the squat and leg press and fewer on the deadlift, so treat the result as a starting point and adjust after a few sessions.
How often should I retest my one rep max?
Every 4 to 8 weeks is enough for most training plans. Re-enter a recent hard set rather than testing an actual max; a set of 3 to 5 reps taken close to failure gives a reliable estimate with far less fatigue and risk.