One Rep Max Calculator
Estimate your one-rep max from the weight and reps of a set, with training percentages.
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How to do it
- 1Fill in the boxes
Type your numbers or pick the options you need.
- 2See the result
The answer updates right away as you change a value.
- 3Use it
Copy the result or note it down. Nothing is sent anywhere.
About this tool
Enter the weight you lifted and the number of reps you completed (up to 30). The tool estimates your one-rep max (1RM) using the Epley and Brzycki formulas and shows 90, 80, 70 and 60 percent loads for training.
The formulas
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). Results are most accurate for sets of 10 reps or fewer.
Example
Lifting 80 kg for 8 reps gives an estimated 1RM of about 101 kg. Working at 80 percent is then around 81 kg.
Safety
A calculated max is an estimate. Test heavy singles only with a spotter and good form, and build up gradually.
Frequently asked questions
Which formula is better?
Both are close. The tool averages Epley and Brzycki.
How many reps should I use?
Sets of 3 to 8 reps give the most accurate estimates.
Is it safe to lift a true 1RM?
Only with a spotter and proper warm-up. Many lifters use the estimate instead.
What percent should I train at?
Strength work is often 80 to 90 percent, hypertrophy 65 to 80 percent.