One Rep Max Calculator
Your one-rep max is the heaviest weight you can lift for one clean repetition on a specific movement. It is the reference point behind percentage-based strength work, but testing it directly can be tiring and risky. Enter a recent submaximal set, and the calculator estimates a practical 1RM with the Epley, Brzycki and Lander formulas.
How to estimate your 1RM
-
1
Use a recent hard set
Choose a set close to failure but before form breaks down. A 3-6 rep set usually gives the cleanest estimate.
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2
Enter weight and reps
Use kg or lb consistently, then enter completed reps as a whole number.
-
3
Compare three formulas
Epley, Brzycki and Lander will not match exactly, so treat the spread as a useful confidence range.
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4
Program conservatively
Use the average or the lower estimate when planning heavy work, especially if the set was above 8-10 reps.
Formulas this calculator uses
| Formula | Equation | Best used with |
|---|---|---|
| Epley | 1RM = w · (1 + r / 30) |
2-10 reps |
| Brzycki | 1RM = w · 36 / (37 − r) |
1-10 reps |
| Lander | 1RM = 100 · w / (101.3 − 2.67123 · r) |
1-10 reps |
Where w is the weight lifted and r is the number of completed reps. The unit does not change the math: kg stays kg, lb stays lb.
Percentage of 1RM for common rep ranges
| Reps | Approx. %1RM |
|---|---|
| 1 | 100% |
| 2 | 95% |
| 3 | 93% |
| 5 | 87% |
| 8 | 78% |
| 10 | 75% |
| 12 | 70% |
| 15 | 65% |
Which estimate to use
- Brzycki is usually the most conservative in the low-to-mid rep range.
- Epley is simple and often a little higher below 10 reps.
- Lander works well as a third check because it usually sits close to the other two.
For powerlifting-style programming, base the estimate on a controlled 3-5 rep set and be cautious with jumps. For hypertrophy blocks, a 6-10 rep set can be useful, but the average should be treated as a training number, not a guaranteed max.
Tips for honest numbers
- Do not pad reps. Count only reps completed with the same technique you want to program from.
- Match the movement. A high-bar squat, low-bar squat and front squat each need their own 1RM estimate.
- Keep units consistent. If your program uses kg, enter kg; if it uses lb, enter lb.
- Use safeties for real max attempts. A spotter, rack pins or safety arms matter most on bench press and squat attempts.
Frequently Asked Questions
They are usually within about 5-10% of a true 1RM when based on a near-failure set of 3-6 clean reps. Above 10 reps, the error grows because strength endurance varies a lot from lifter to lifter.
Occasionally, if maximal singles are part of your sport or training plan. For general strength, fitness or hypertrophy work, estimated 1RM percentages are often enough and carry less risk.
Each formula was fitted from different data and makes a different assumption about how repetitions relate to maximum strength. The spread is a reminder that 1RM estimates are planning tools, not exact measurements.
They work best for compound barbell lifts such as bench press, squat, deadlift and overhead press. They are less useful for isolation work, where local fatigue and technique can distort the rep-to-max relationship.
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