Free calculator
One rep max (1RM) calculator
Your one rep max is the heaviest weight you can lift for a single rep. Enter the weight and reps from a hard set to estimate it. It works best with a set of about 3–6 reps taken close to failure.
Unit
Reps from 1 to 12. Estimates from sets above 10 reps get rough.
If you stopped with reps left, the RPE calculator takes that into account.
Enter a weight and reps to see your estimated 1RM.
1RM percentage chart
Programs often set training weights as a percentage of your 1RM, such as 5 sets of 5 at 80%. The reps column is the Epley formula run backwards: roughly how many reps you can do at that percentage before failure. Enter a set above to fill in your loads.
From 70% down, the reps column goes past the 12 reps this calculator accepts, so treat those rows as rough. To see which plates make up a load, use the plate calculator.
| % of 1RM | Reps to failure |
|---|---|
| 100% | 1 |
| 95% | 2 |
| 90% | 3 |
| 85% | 5 |
| 80% | 8 |
| 75% | 10 |
| 70% | 13 |
| 65% | 16 |
| 60% | 20 |
| 55% | 25 |
| 50% | 30 |
Epley vs Brzycki vs Lombardi
Each formula turns the weight and reps of one set into an estimated max.
- Epleyweight × (1 + reps ÷ 30)
- Brzyckiweight × 36 ÷ (37 − reps)
- Lombardiweight × reps0.10
At 1 rep all three give the weight you lifted. From 2 to 10 reps they stay within 6% of each other, but the highest one changes: Lombardi at 2–5 reps, Epley at 6–9, Brzycki from 11 up (it ties Epley at 10). Past 10 reps they split quickly. Here is what each one estimates from a set of 100 kg:
| Reps at 100 kg | Epley | Brzycki | Lombardi |
|---|---|---|---|
| 1 | 100 | 100 | 100 |
| 2 | 106.7 | 102.9 | 107.2 |
| 3 | 110 | 105.9 | 111.6 |
| 4 | 113.3 | 109.1 | 114.9 |
| 5 | 116.7 | 112.5 | 117.5 |
| 6 | 120 | 116.1 | 119.6 |
| 7 | 123.3 | 120 | 121.5 |
| 8 | 126.7 | 124.1 | 123.1 |
| 9 | 130 | 128.6 | 124.6 |
| 10 | 133.3 | 133.3 | 125.9 |
| 11 | 136.7 | 138.5 | 127.1 |
| 12 | 140 | 144 | 128.2 |
None of them is the most accurate for everyone. Pick one and use it every time, so this month's estimate compares cleanly with last month's. This calculator leads with Epley and uses it for the rep maxes and the percentage chart.
Questions about 1RM estimates
How accurate is an estimated 1RM?
It depends on you and the lift. People differ in how many reps they can do at the same share of their max: a 2024 meta-regression of 952 tests found a between-person standard deviation of about 2.5 reps at 80% of 1RM and about 4.4 reps at 60%. That spread grows as the weight gets lighter, so an estimate from a set of 3–6 reps is more useful than one from a set of 10 or more.
What if I didn't take the set to failure?
The formulas assume you couldn't have done another rep, so a set with reps left in the tank gives a low estimate. Add the reps you had left to the rep count: 100 kg for 5 with 2 left is roughly a 7-rep max. The RPE calculator does this from the set's RPE. Guesses of reps left are more accurate close to failure, so a set that stopped 1–2 reps short gives a better estimate than one that stopped 5 short.
Should I test a true 1RM instead?
Only if you need the real number, for example before a powerlifting meet. A max attempt needs a long warm-up, a spotter or safety arms, and a day when you're fresh. For setting training weights an estimate is usually enough: programs such as 5/3/1 base their percentages on a training max set below your true max anyway.
Does the calculator work for any exercise?
The math works for any weight and rep count, but the number of reps you can do at a given percentage differs between exercises. In the same 2024 meta-regression, people did more reps on the leg press than on the bench press at the same percentage of their max. Use an estimate to compare a lift with itself over time, not to compare two different lifts.
Why does the calculator stop at 12 reps?
Past 10 reps the formulas stop agreeing. From 100 kg for 12 reps, Brzycki estimates 144 kg and Lombardi 128.2 kg. At 20 reps Brzycki gives 211.8 kg, more than twice the weight on the bar. For a usable estimate, enter a heavier set of 10 reps or fewer.
Related
RPE calculator
CalculatorTurn weight, reps and RPE into an estimated 1RM, then get the load for any reps and RPE you're aiming for.Barbell plate calculator
CalculatorSee which plates go on each side of the bar for any target weight, in kg or lb.How to track progressive overload
ArticleWhat to write down after each set and how to decide when to add weight or back off, with a double progression example in kg and the rule PRGRES uses to suggest your next set.
Get the app
I build PRGRES, a workout tracker for iPhone and iPad. It uses the same Epley formula for the estimated 1RM on its progress charts, PRs and Strength Leagues.
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