One Rep Max Calculator
Estimate your one-rep max — the most you could lift once — from a weight and reps, with the percentage table for programming.
Your strength, without maxing out
A one-rep max is the heaviest weight you could lift for a single repetition, the standard measure of strength in the gym. Actually testing it is risky and taxing, so instead this estimates it from a weight you lifted for several reps — a safer way to gauge your max and plan training around it.
How it's estimated
The estimate uses the well-established relationship between the weight lifted and the number of reps: the more reps you can do with a weight, the further below your true max that weight is. Established formulas turn a set — say, a weight for five reps — into an estimated single max.
More reps at a weight -> that weight is further below your maxA weight for ~5 reps is roughly 87% of a 1-rep maxThe percentage table for training
The real use of a one-rep max is programming — most strength training prescribes weights as a percentage of it. This table shows the rough relationship between percentage of max and the reps typically possible:
| % of 1-rep max | Reps roughly possible |
|---|---|
| 100% | 1 |
| 95% | 2 |
| 90% | 4 |
| 85% | 6 |
| 80% | 8 |
| 75% | 10 |
| 70% | 12 |
So a program calling for sets at 80% points you to a weight you could manage for about eight reps. The estimate is least accurate at high rep counts, where the relationship breaks down, so it is most reliable from sets of around five reps or fewer. This is general fitness information; lift within your ability, use good form and a spotter for heavy work, and consult a professional if you are new to training or have any injury concern.
One Rep Max Calculator FAQ
How is a one-rep max estimated?
From a weight you lifted for several reps — the more reps you can do with a weight, the further below your max it is. Formulas turn a set into an estimated single max.
Why estimate instead of testing it?
Testing a true one-rep max is risky and taxing. Estimating from a moderate set is safer and, from around five reps or fewer, reasonably accurate.
What is a one-rep max used for?
Programming — most strength training prescribes weights as a percentage of it, so knowing it sets your working weights across a program.
Is the estimate always accurate?
It is least accurate at high rep counts, where the relationship breaks down, so it is most reliable from sets of about five reps or fewer.
Is my data uploaded?
No. The calculation happens in your browser.