AI-generated imageFree tools · Updated 2026-10-22
One-rep max calculator
Enter a weight and how many clean reps you did with it, and this estimates the most you could lift once. It averages the Epley and Brzycki formulas, which are most reliable for sets of 10 reps or fewer, and shows the weights to use at each percentage of your max.
212 lb estimated one-rep max
Based on 5 reps. Estimates are most reliable at 10 reps or fewer.
| Percent of max | Weight | About how many reps |
|---|
How it works
Two formulas do the work. Epley multiplies the weight by 1 plus the reps divided by 30. Brzycki multiplies the weight by 36, divided by 37 minus the reps. Both were built from people lifting to failure, and they agree closely for low reps. This calculator shows their average, rounded to the nearest whole number.
One rep is not an estimate, so a single is shown as is. Above 12 reps the formulas get unreliable, so the calculator stops there.
How to use your number
Most programs set weights as a percentage of your max. Lighter percentages suit more reps, heavier ones suit fewer. The table gives the usual pairings. They vary from person to person, so use them as a starting point and adjust by how the sets feel.
Recalculate every few weeks from a recent hard set. If your estimate keeps rising, your program is working.
Getting a good estimate
- Use a set that was hard but clean. Reps with broken form overstate your strength.
- Use the lowest-rep hard set you did recently. A set of 3 to 6 gives a better estimate than a set of 12.
- Estimate each lift on its own. A bench press number tells you nothing about your squat.
- Compare like with like: the same lift and depth, on the same equipment.
Also asked
How accurate is a one-rep max calculator?
For sets of about 10 reps or fewer, the common formulas usually land within a few percent of a tested max. Above about 10 reps they drift further, because endurance starts to matter as much as strength. Treat the number as a planning estimate, not a record.
Should I test my real one-rep max?
You don't need to. Most people train well using an estimate from a hard set of 3 to 8 reps. If you do test a true max, warm up fully and use safety pins or a spotter. Stop if your form breaks down.
Which formula does this calculator use?
It averages two of the most widely used formulas, Epley and Brzycki. They agree closely for low reps and spread apart as reps go up.
What weight should I use for sets of 5?
Many programs use about 80 to 85 percent of your one-rep max for sets of 5. The table under the calculator shows the weights for your number.