Free Tool
Lift any weight for any reps - find your estimated one rep max and full 1–10RM table instantly.
Track your progress
The web calculator gives you today's estimate. The app saves every result so you can see your strength curve over weeks and months.
Your 1 Rep Max (1RM) is the maximum weight you can lift for a single repetition with good form. It's the universal standard for measuring strength across powerlifting, weightlifting, and CrossFit.
This calculator uses the Epley formula: 1RM = weight × (1 + reps ÷ 30). It's one of the most widely validated 1RM prediction formulas, accurate for rep ranges of 1–10. Beyond 15 reps, accuracy decreases as other factors (muscular endurance, cardio) play a larger role.
Training percentages are typically based on your 1RM. Strength work sits around 85–95%, hypertrophy at 70–85%, and endurance work below 70%. Use the table above to find the right weight for your training goal today.