One rep max calculator
Enter the weight and reps of a hard set. You get your estimated one rep max (1RM), the weight to use at each percentage, and an RPE based estimate if you track effort.
kglb
Estimated one rep max, the average of three formulas.
The RPE chart covers 1 to 12 reps. Lower the reps or clear the RPE.
Above 10 reps the formulas drift apart and get less reliable. A set of 3 to 8 hard reps gives a better estimate.
Percentage chart
Weights are rounded to the nearest 2.5 kg5 lb. Reps are roughly how many you could do at that load if you went to failure.
| Percent of 1RM | Weight (kglb) | Reps, about |
|---|
How the estimate works
Each formula turns one submaximal set into a guess at the most you could lift once. They were fitted on different groups of lifters, so they agree near 1 to 5 reps and drift apart as reps go up. We show all three and use their average as the headline number.
- Epley: weight × (1 + reps / 30)
- Brzycki: weight × 36 / (37 − reps)
- Lombardi: weight × reps0.1
For a single rep, all three return the weight you lifted. The calculator accepts up to 20 reps, but estimates from sets above 10 reps are rough.
Using RPE
RPE (rate of perceived exertion) rates how close a set was to failure. RPE 10 means no reps left, RPE 8 means about two left. If you add an RPE, the calculator also looks up your set in the RPE chart popularized by Mike Tuchscherer of Reactive Training Systems, which accounts for the reps you had left. A set of 5 at RPE 8 counts as about 81 percent of your max. This works best when your RPE ratings are honest and practiced.
Limits
These are estimates. Technique, fatigue, the lift itself and your training history all shift the real number. People with a lot of endurance can do more reps at a given percentage, so formulas often overestimate their max. Test a true max only with good technique and a spotter or safety bars.
Questions
Which one rep max formula is most accurate?
No single formula wins for everyone. Studies comparing them find they are all close for sets of up to about 5 reps and spread out after 10. Averaging several, as this page does, smooths out the bias of any one.
How many reps should I use to estimate my 1RM?
A hard set of 3 to 5 reps gives the most reliable estimate. Sets of 10 or more reps say more about muscular endurance than about your max.
What percentage of my 1RM should I train at?
For strength, most programs use 75 to 90 percent for 3 to 8 reps. For muscle growth, a wide range works, from about 30 to 85 percent, as long as sets end close to failure. The chart above gives the weights for each percentage.
Is it safe to test my real one rep max?
For trained lifters with good technique and safety bars or a spotter, usually yes. Beginners get most of the benefit from estimating instead. This is general information, not medical advice.
Does the calculator work for every lift?
It works best for big barbell lifts like the squat, bench press and deadlift. It is less reliable for small isolation exercises and machines.
Track it over time
A single estimate is a snapshot. Marrow logs your lifts with sets and reps and tracks your estimated one rep max per lift over time from the sets you log, so you can see whether it is moving.
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