One Rep Max Calculator
Estimate your one-rep max (1RM) from any weight and reps using the Epley and Brzycki formulas, in kg or lb, with a percentage table.
Reviewed by Dany, RightSums team · Updated
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health · Daily life · UK & US
Enter the weight you lifted and how many clean reps you managed, in kilograms or pounds. The calculator estimates your one-rep max (1RM), the most you could lift once, with two published formulas. Epley multiplies the weight by 1 plus 0.0333 times the reps. Brzycki divides the weight by 1.0278 minus 0.0278 times the reps. You see both results, their average and a table of training weights from 50% to 100% of your 1RM in both kg and lb. Research on these formulas found them most accurate at 10 reps or fewer, so the tool warns you above that. It is an estimate for planning sessions, not medical or coaching advice.
Accepted inputs
- Weight lifted in kg or lb
- Reps completed (1 to 30)
Outputs
- Epley 1RM estimate
- Brzycki 1RM estimate
- Average 1RM in kg and lb
- Training weights from 50% to 100% of 1RM
How to use the One Rep Max Calculator
- Choose kilograms or pounds, then enter the weight you lifted and the number of reps you completed with good form.
- The calculator applies the Epley formula, weight × (1 + 0.0333 × reps), and the Brzycki formula, weight ÷ (1.0278 − 0.0278 × reps).
- It shows both estimates and their average, and a single rep simply returns the weight you lifted.
- A table then turns the average into training weights from 50% to 100% of your one-rep max in both kg and lb.
Frequently asked questions
How do I calculate my one rep max?
Take a weight you can lift for 10 reps or fewer and put it into a formula. For 100 kg lifted 5 times, Epley gives 100 × (1 + 0.0333 × 5) = 116.7 kg and Brzycki gives 100 ÷ (1.0278 − 0.0278 × 5) = 112.5 kg. The average is 114.6 kg, or about 252.6 lb.
What is my 1RM if I bench 225 lb for 5 reps?
About 258 lb. Epley puts it at 262.5 lb and Brzycki at 253.2 lb, so the average is 257.8 lb, which is 116.9 kg. Working at 80% of that means about 206 lb. Treat it as an estimate: your true single can differ, so build up to heavy lifts gradually.
Which is more accurate, Epley or Brzycki?
Neither is always right. The two give almost the same answer at 10 reps: 60 kg for 10 reps is 80.0 kg on both. At low reps Epley reads a little higher. Above 10 reps they drift apart, so 60 kg for 15 reps gives 90.0 kg with Epley and 98.2 kg with Brzycki. That is why the calculator shows both and the average.
Is a 1RM calculator accurate for high reps?
Less so. A 2006 study in the Journal of Strength and Conditioning Research found every formula it tested was less accurate from a 10-rep set than a 5-rep set, and advised using no more than 10 reps. For the best estimate, use a weight you can lift between 2 and 10 times with good form.
What percentage of my 1RM should I train at?
That depends on your goal and experience, so follow your coach or programme. The calculator shows 50% to 100% in 5% steps. With an estimated 1RM of 114.6 kg, 70% is 80.2 kg and 85% is 97.4 kg. In pounds, a 180 lb 1RM from 135 lb for 10 reps gives 144 lb at 80%.
Sources
The rates and rules in this tool come from:
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