LiftonicOne-rep max calculator
Enter a weight and how many reps you did with it, and this estimates the most you could lift once. It averages the Epley and Brzycki formulas, which are most accurate from sets of 10 reps or fewer.
How it works
A one-rep max (1RM) is the most weight you can lift for a single rep with good form. Rather than testing it, you can estimate it from a set of several reps, which is safer and gives a good enough number to plan training around.
This calculator uses two well-known formulas and shows their average:
- Epley (1985): 1RM = weight × (1 + reps ÷ 30).
- Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps).
The two formulas agree closely between 2 and 10 reps, and they drift apart as reps go up, so the estimate is most useful from a hard set of 10 reps or fewer. Sets taken to failure give a better estimate than sets with reps left in the tank. The rep counts in the table come from the Epley formula run backwards, and the weights are rounded to the nearest 2.5 kg or 5 lb so you can load them.
Questions
How accurate is a one-rep max calculator?
From a hard set of 10 reps or fewer, the estimate usually lands within a few percent of a tested max. It gets less reliable with higher reps, and some people are naturally better at high reps than others.
Which formula is best, Epley or Brzycki?
Neither is best for everyone. They give nearly the same answer at low reps, which is why this calculator shows their average and both numbers.
Should I test my real one-rep max?
You don't need to. Most programs work from percentages, and an estimate from a set of 3 to 5 reps is close enough. If you do test, warm up well and use safeties or a spotter.
What percentage of my max should I train with?
Sets of 5 are usually done around 80 to 85 percent of your max, and sets of 8 to 10 around 70 to 75 percent. The table under the calculator shows the weights for your estimate.
Link to this calculator
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