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About the one rep max calculator
Your one-rep max (1RM) is the heaviest weight you can lift once. Testing it is hard and can be risky. This calculator estimates it from a normal set: type the weight lifted and the reps done.
You get your estimated one-rep max, the result of six well-known formulas (Epley, Brzycki, Lander, Lombardi, Mayhew and O'Conner), and a percent chart that shows what weight to use for each percent of your max.
How to use it
- Type the weight lifted and the reps done — or press 1, 3, 5, 8 or 10 reps
- Open More options to choose kg or lb
- Read your estimated 1RM, then the six formulas
- Use the chart under it for your training weights
For the best estimate, use a hard set of 2 to 10 reps, done with good form and as close to failure as is safe.
The formulas
With w = the weight and r = the reps:
| Formula | Calculation |
|---|---|
| Epley | w × (1 + r ÷ 30) |
| Brzycki | w × 36 ÷ (37 − r) |
| Lander | 100 × w ÷ (101.3 − 2.67123 × r) |
| Lombardi | w × r^0.10 |
| Mayhew | 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r)) |
| O'Conner | w × (1 + 0.025 × r) |
The calculator shows the average of all six, which is a steady guide.
Example: 100 kg for 5 reps
| Formula | 1RM |
|---|---|
| Epley | 116.7 kg |
| Brzycki | 112.5 kg |
| Lander | 113.7 kg |
| Lombardi | 117.5 kg |
| Mayhew | 119.0 kg |
| O'Conner | 112.5 kg |
| Average | 115.3 kg |
Percent chart
| % of 1RM | About how many reps |
|---|---|
| 100 % | 1 |
| 95 % | 2 |
| 90 % | 4 |
| 85 % | 6 |
| 80 % | 8 |
| 75 % | 10 |
| 70 % | 12 |
| 65 % | 16 |
| 60 % | 20 |
How to use the percents
- Strength: 1–5 reps at 85–95 %
- Muscle size: 6–12 reps at 67–85 %
- Endurance: 15 or more reps at 60 % or less
Ask a coach to plan the full program, and warm up well before heavy sets.
Frequently asked questions
How do I calculate my one rep max?
Do a hard set, note the weight and the reps, and type them in. Or use a formula: Epley is weight × (1 + reps ÷ 30).
Which formula is the most exact?
They agree well for 2 to 10 reps and drift apart above that. That is why the calculator shows the average.
Is it safe to test a real 1RM?
It can be, with a spotter, a good warm-up and good form. The estimate is a safer way to know your level.
Does it work for every lift?
It is best for big lifts like the bench press, squat and deadlift. For small exercises, the result is less exact.
Why is my real max different?
Technique, rest, mood and the exercise all change it. Treat the number as a good guide, not as a promise.
Is this medical advice?
No. It is a general guide. Lift safely and ask a coach or doctor if you are not sure.
Good to know
- Your numbers are saved only in this browser
- Nothing you type is sent anywhere
- The weights are rounded to the nearest half unit (0.5 kg or 0.5 lb)
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