One Rep Max Calculator
Estimate your 1RM from any submaximal set using 4 proven formulas.
About this tool
Enter the weight you lifted and how many reps you completed on any submaximal set (bench, squat, deadlift, or any lift). The calculator estimates your one-rep max using four formulas — Epley, Brzycki, Lombardi, and O'Conner — then averages them for a reliable estimate. The percentage table shows exactly what weight to use for any rep range.
How to use it
Quick steps to get the most out of this utility.
- 1
Enter the weight
Input the weight you lifted on your most recent submaximal set.
- 2
Enter the reps
Enter how many reps you completed with good form. 5 or fewer gives the most accurate estimate.
- 3
Read your 1RM
The average of four formulas gives a balanced estimate. Use the percentage table to plan your training.
How 1RM formulas actually work
All 1RM formulas are based on the same observation: the number of reps you can perform at a given weight follows a predictable curve. Epley (1985) observed that for each additional rep beyond one, the effective load decreases by about 2.5%. Brzycki (1993) modeled it as a linear drop-off. The differences between formulas are small for low-rep sets and grow as reps increase.
The practical takeaway: test with 3–5 reps, not 10. A set of 135 lb for 5 reps tells you far more about your true max than 100 lb for 15 reps. The calculator is most useful as a programming tool — use the percentage chart to set your working weights for any rep scheme.
Frequently asked questions
What is a one-rep max?+
A one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It is the universal standard for measuring and comparing strength in weightlifting, powerlifting, and strength training.
Why use a 1RM calculator instead of testing it?+
Testing your true 1RM requires a spotter, perfect technique, and carries a real injury risk — especially for beginners. A submaximal set of 3–5 reps is safer, easier to perform, and the formula estimates are accurate within 3–5% for most lifters.
How accurate are 1RM formulas?+
For sets of 5 reps or fewer, the Epley and Brzycki formulas are typically within 3–5% of the true value for experienced lifters. Accuracy drops as reps increase — estimates from a 10-rep set are less reliable. This calculator averages four formulas (Epley, Brzycki, Lombardi, O'Conner) for a more robust estimate.
Which formula is best?+
Epley is the most widely used and works well for 1–10 reps. Brzycki is conservative and safer. Lombardi tends to estimate higher. The average of all four gives a balanced estimate most lifters find realistic.
How do I use the percentage breakdown?+
Once you know your estimated 1RM, use the percentage chart to program your training. For strength: work at 85–95% (3–5 reps). For hypertrophy: 75–85% (5–8 reps). For endurance: 65–75% (8–12 reps). The chart shows the exact weight for each percentage.
Keep exploring
More utilities and reading from Toolisk.