One Rep Max Calculator
Estimate the heaviest weight you could lift once (your 1RM) from a set of 1 to 12 reps, and see what 50 to 95% of it is. The math runs in your browser: nothing you type is sent anywhere.
Your estimated 1RM
Fill in the weight and reps of one set and press Calculate to see your estimated 1RM and a percentage chart for your training weights.
- Estimated 1RM (Epley)
- Estimated 1RM (Brzycki)
- 95% of 1RM
- 90% of 1RM
- 85% of 1RM
- 80% of 1RM
- 75% of 1RM
- 70% of 1RM
- 65% of 1RM
- 60% of 1RM
- 55% of 1RM
- 50% of 1RM
These are estimates, not medical or dietary advice. How we estimate, with sources
How 1RM is estimated
Two common formulas turn one set into an estimated max. Epley multiplies the load by 1 plus the reps divided by 30. Brzycki multiplies the load by 36 and divides by 37 minus the reps. A single rep is already your max, so for 1 rep the calculator returns the load itself.
For example, 185 lb for 5 reps gives about 216 lb by Epley and 208 lb by Brzycki. In kilograms, 80 kg for 10 reps gives about 106.5 kg by both, because the two formulas meet at 10 reps.
Using 1RM percentages in training
Programs often set loads as a share of your max. Your result shows 50 to 95% of your estimated 1RM. The table below shows about how many reps each heavier share allows, by the Epley formula.
A position stand from the American College of Sports Medicine recommends loads you can lift 8 to 12 times for beginners. For trained people it recommends 1 to 12 reps over a program, leaning on heavy sets of 1 to 6 for strength and on 6 to 12 for muscle size, and 40–60% of 1RM for more than 15 reps for endurance. Treat these as ranges to start from.
| Share of 1RM | Estimated reps |
|---|---|
| 95% | 2 |
| 90% | 3 |
| 85% | 5 |
| 80% | 8 |
| 75% | 10 |
Why estimates get less accurate above about 10 reps
The formulas assume each extra rep stands for a fixed drop in load, which holds best for heavy sets. In a study comparing predictions, sets of 5 reps predicted the max more accurately than sets of 10 or 20. In long sets, endurance and fatigue matter more. That is why this calculator accepts 1 to 12 reps.
1RM test vs estimate
A 1RM test means working up to one heaviest rep with good form, usually after warm-up sets. It measures your max directly on that day. An estimate uses a set you have already done, so you get a starting number without a maximal attempt. Both change as you train, so check again every few weeks.
Track your lifts
Logging every set shows how your estimated 1RM changes over time. The BodyMacros app logs your lifts next to your food, uses the same Epley estimate for each lift, and lets the days you train shape your protein and calorie estimates.
FAQ
How do I calculate my one rep max?
Take a recent set you did with good form, ideally 2 to 10 reps, and put the load and reps into a formula. Epley multiplies the load by 1 plus the reps divided by 30, so 100 kg for 5 reps estimates about 116.5 kg. This calculator does the math for you and shows it as an estimate.
Epley vs Brzycki: which formula should I use?
Either works for sets of up to about 10 reps. They give the same result at exactly 10 reps; below that Epley reads a little higher, above it Brzycki does. This calculator shows both and uses Epley for the percentage chart, the same formula the app uses for your estimated 1RM on each lift.
How do I convert a 3-rep max to a 1-rep max?
Multiply your 3-rep max by about 1.1 with the Epley formula, or by about 1.06 with Brzycki. For a 5-rep max, the factors are about 1.17 and 1.13. For example, 100 kg for 3 reps estimates 110 kg by Epley. Enter 3 or 5 as your reps above to get both numbers at once.
Does the calculator work for bench press, squat and deadlift?
Yes. The formulas only use the load and the reps, so the same calculation works for the bench press, the squat, the deadlift or any other lift. Enter a recent set from the lift you want to estimate, and keep one estimate per lift, because your max is different on each one.
How accurate is a 1RM calculator?
It is an estimate, and it is closest when the set is heavy. In one study, predictions from a 5-rep max were more accurate than predictions from 10 or 20 reps. A set done with good form close to failure also helps. Above about 10 reps the error grows, so this calculator accepts up to 12 reps.
What is 1RM?
1RM, or one-rep max, is the heaviest load you can lift once with good form in a given exercise. Programs use it to set training weights as percentages, such as 80% of 1RM. You can test it directly or estimate it from a lighter set with more reps, which is what this calculator does.
What is a 1RM test?
A 1RM test means working up to the heaviest single rep you can complete with good form, usually after several warm-up sets. It measures your max directly. This calculator estimates the same number from a lighter set you have already done, so you get a starting point without attempting a maximal lift.
What percentage of 1RM should I use for muscle growth?
A position stand from the American College of Sports Medicine recommends, for muscle size, loads you can lift 1 to 12 times over a program, with most sets at 6 to 12 reps. By the Epley formula, 6 to 12 reps is roughly 70 to 85% of your 1RM. Treat it as a range to start from.
Track this in the app
Log your food and your lifts in one place. Your estimates adjust each week to how you eat and train.
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