One Rep Max Calculator
Calculate your 1RM (One Rep Max) based on your lifted weight and repetitions. Estimate your maximum strength strength potential and find training percentages for Bench Press, Squat, and Deadlift.
For best accuracy, use reps between 1 and 10.
What is a One Rep Max (1RM)?
Your One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It is the gold standard for measuring raw strength in exercises like the Squat, Bench Press, and Deadlift.
Testing your true 1RM in the gym can be dangerous and fatiguing. This 1RM calculator allows you to estimate your max safely by using a weight you can lift for multiple repetitions (e.g., 3, 5, or 10 reps) and applying validated mathematical formulas.
How to use this calculator
- Select Weight: Pick a weight you are comfortable lifting for multiple reps.
- Perform Reps: Perform the exercise until failure (or near failure) with good form.
- Input Data: Enter the weight and the number of reps you completed into the calculator above.
Note: The calculator is most accurate when the rep count is low (between 1 and 10). Performing high-rep sets (15+) tests endurance more than raw strength, making the 1RM estimate less precise.
Training Zones based on 1RM
Knowing your max allows you to program your training effectively using percentage-based zones:
- Strength (85-100%): Low reps (1-5). Focuses on neurological efficiency and raw power.
- Hypertrophy (70-85%): Moderate reps (6-12). The "bodybuilding" zone, ideal for muscle growth.
- Endurance (50-70%): High reps (12+). Improves muscular stamina and cardiovascular conditioning.
The Formulas
We use several popular formulas to ensure accuracy. The primary result displayed is based on the Epley formula, which is widely considered accurate for general lifters.
- Epley: $1RM = w \times (1 + r/30)$
- Brzycki: $1RM = w / (1.0278 - 0.0278 \times r)$
If your goal is to change your body composition along with your strength, check out our Macro Calculator or Body Fat Calculator.
? Frequently Asked Questions
Yes, for most people, calculated 1RMs are within 5-10% of their true max, especially if the rep range used for testing is under 10. It is a safe way to track progress without maxing out every week.
The Epley and Brzycki formulas are the most popular. Epley tends to be slightly better for high-rep estimates, while Brzycki is often used for lower rep ranges (under 10).
1RM calculators are most accurate for compound lifts (Squat, Bench, Deadlift, Overhead Press). They are less reliable for isolation moves like curls or lateral raises where form breaks down easily.
You don't need to test your true 1RM often. You can use this calculator to update your 'estimated' max every training cycle (4-8 weeks) based on your best working sets.