One Rep Max Calculator (1RM)
Enter a weight you lifted and how many reps you managed. You get an estimate of your one rep max (1RM), the most you could lift once, and a table of training weights worked out from it.
Free, no sign-up. What you enter stays in your browser: it is not saved or sent to HerFound. Reviewed .
Units
Full reps with good form, from 1 to 12.
Enter the weight you lifted and the reps you completed.
How it works
The calculator uses two well known formulas. Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 minus reps). For a single rep, both give the weight you lifted.
For 100 kg lifted 5 times, Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg and Brzycki gives 100 × 36 ÷ 32 = 112.5 kg. The headline number is the average of the two, here 114.6 kg. Both results are shown so you can see how far apart they are.
The training table takes 95, 90, 85, 80, 75, 70, 65 and 60% of the average and rounds each one to the nearest 0.5 kg or 1 lb, so you can load it on a bar.
What it cannot tell you
- It is an estimate. It is most accurate from a hard set of 2 to 6 reps and gets less accurate above about 10 reps, which is why this calculator stops at 12.
- The result differs by lift and by lifter. Formulas tend to fit squat, bench press and deadlift better than small or single-arm lifts, and people who train with high reps often get more reps at a given percentage.
- Do not test a true one rep max alone. Use a spotter or safety bars, warm up first, and stop if your form breaks down.
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Common questions
To calculate your one rep max, multiply the weight you lifted by (1 + reps ÷ 30). This is the Epley formula. If you lifted 60 kg for 10 reps, your estimated one rep max is 60 × (1 + 10 ÷ 30) = 80 kg.
Neither the Epley nor the Brzycki formula is more accurate for everyone. They give the same answer at 10 reps and are within a few percent of each other below that, with Epley a little higher. Taking the average of the two is a common way to settle the difference.
Use a set of 2 to 6 reps to estimate your one rep max, taken close to the point where you could not do another rep with good form. The more reps in the set, the less accurate the estimate. Above about 10 reps the formulas become unreliable.
The percentage of your one rep max to lift depends on the goal of the set. As a general guide, 80 to 90% for sets of 3 to 6 reps builds maximum strength, and 65 to 80% for sets of 6 to 12 reps is common for building muscle. Start at the lower end if you are new to lifting.
A one rep max calculator uses the same formula for women and men. The formulas work from the weight and reps you enter, not from your sex or body weight. Some studies find women can do more reps at a given percentage, so an estimate from a high-rep set may come out a little high.