One Rep Max Calculator
| 90% | 80% | 70% | 60% |
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Please enter valid weight and reps (1-15).
What Is a One Rep Max Calculator?
A one rep max (1RM) calculator estimates the maximum weight you could lift for a single repetition, based on a weight you've lifted for multiple reps. It's used to program training percentages without needing to test a true max lift, which carries higher injury risk.
Formula Used (Epley Formula)
1RM = Weight × (1 + Reps ÷ 30)
This formula is one of the most widely used estimation methods in strength training and works best for rep ranges under about 10-12.
How to Use This Calculator
Enter the weight you lifted and how many reps you completed with good form. Click "Calculate 1RM" to see your estimated one rep max along with common training percentages (60-90%) for programming purposes.
Frequently Asked Questions
How accurate is an estimated 1RM?
Estimation formulas are reasonably accurate for rep ranges of 10 or fewer, but accuracy decreases for higher rep sets since fatigue affects the relationship differently.
Why do I need training percentages?
Most strength programs prescribe work at specific percentages of your 1RM (e.g., 80% for strength, 60% for hypertrophy), so knowing your estimated max helps you load the bar correctly.
Should I actually test my true 1RM?
Testing a true 1RM carries injury risk and isn't necessary for most training goals — estimation formulas are generally sufficient for programming purposes.
Does this work for any exercise?
It works best for compound barbell lifts like squat, bench press, and deadlift, where the strength curve is well-studied. Accuracy may vary for other movements.