Strength
One Rep Max Calculator
Calculate your 1RM using 7 established strength formulas
Lift Information
Fill out the form to see your estimated 1RM
Calculate your 1RM using 7 established strength formulas
Fill out the form to see your estimated 1RM
Your One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's the gold standard for measuring strength, used by powerlifters, coaches, and athletes worldwide.
Rather than actually testing your true 1RM (which carries injury risk), this calculator estimates your maximum based on the weight you lifted for multiple reps. Using 7 peer-reviewed formulas - including Epley (1985) and Brzycki (1993) - it provides a practical estimate you can use to program your training.
Knowing your estimated 1RM allows you to train with precise percentages. Whether you're working on strength (85-95%), hypertrophy (70-85%), or endurance (60-70%), you'll have a practical percentage-based target to guide your working sets.
Estimating your 1RM from submaximal lifts is safer than frequent true max testing. It helps set training percentages, track strength over time, and program workouts without the injury risk of heavy singles. The 7-formula average provides a more stable estimate than any single formula alone.
Your 1RM tells you how much to lift - but are you doing enough total work? Use our Training Volume Calculator to ensure you're hitting optimal sets per muscle group for maximum growth. Volume × Intensity = Results.
1RM calculators are accurate within 5-10% of your true max when using low rep ranges (1-6 reps). Accuracy decreases as rep count increases.
The formulas used in this calculator were developed through research on trained lifters and have been validated against actual 1RM testing. However, several factors affect individual accuracy:
For best accuracy: Use a weight you can lift for 3-5 reps with perfect form. Test when fresh (not at the end of a workout). By averaging 7 different formulas, this calculator minimizes individual formula errors.
This calculator uses 7 scientifically validated formulas to estimate your 1RM. Each formula was developed through different research and has its own strengths:
| Formula | Year | Best For |
|---|---|---|
| Epley | 1985 | Most widely used, good all-around |
| Brzycki | 1993 | Most accurate for 1-10 reps |
| Lander | 1985 | Conservative estimate |
| Lombardi | 1989 | Power-focused training |
| Mayhew | 1992 | Bench press specific |
| O'Conner | 1989 | Moderate estimate |
| Wathan | 1994 | Higher rep ranges |
No single formula is perfect for everyone. Factors like training experience, muscle fiber composition, exercise technique, and genetics all affect how well each formula predicts your true max. By averaging 7 formulas, this calculator gives you a more reliable estimate than any single formula alone.
All 1RM formulas are most accurate when using 1-6 reps. Accuracy decreases as rep count increases. For the most reliable estimate, enter a weight you can lift for 3-5 reps with good form. Estimates from 10+ reps should be considered rough approximations.
Once you know your estimated 1RM, these common percentage zones can help guide your training. These are typical ranges, not rigid rules - individual response varies:
Reps: 1-5 per set
Sets: 3-6
Rest: 3-5 minutes
Reps: 6-12 per set
Sets: 3-5
Rest: 1-2 minutes
Reps: 12-20+ per set
Sets: 2-4
Rest: 30-60 seconds
1RM calculators are typically within 5-10% of your true max when using 1-6 reps. Accuracy decreases with higher rep counts. Individual factors like training experience, fatigue, technique, and genetics affect accuracy. Use the estimate as a starting point and adjust based on how the weights feel in training.
For most people, testing your true 1RM isn't necessary and carries injury risk. Calculated estimates are sufficient for programming. However, competitive powerlifters and strength athletes may benefit from occasional true 1RM testing - always with proper warm-up, spotters, and technique.
Each formula was developed using different populations, exercises, and methodologies. Some are better for certain exercises (Mayhew for bench press) or rep ranges (Brzycki for low reps). The variance between formulas is typically 2-5%. By averaging multiple formulas, you get a more reliable estimate.
Recalculate your estimated 1RM every 4-6 weeks, or whenever you notice your working weights feeling easier than expected. As you get stronger, your 1RM increases, and your training percentages need to adjust accordingly.
3-5 reps gives the most accurate estimate. At this rep range, the formulas were most extensively validated, and the weight is heavy enough to challenge your max strength without excessive fatigue affecting your performance.
Yes, you have different 1RMs for different exercises. Your squat, bench press, and deadlift 1RMs will all be different. Calculate each exercise separately. The formulas work for any compound exercise, though they were primarily developed using the big three lifts.