One Rep Max (1RM) Calculator
Calculate Your Maximum Strength & Training Percentages
Free one rep max calculator that estimates your maximum lift for any exercise using scientifically-validated formulas. Get personalized weight recommendations for strength, hypertrophy, power, and endurance training.
One Rep Max (1RM) Calculator
A one rep max (1RM) calculator helps you estimate the maximum weight you can lift for a single repetition of any exercise. This tool uses proven formulas from exercise science research to calculate your 1RM and provide specific weight recommendations for different training goals - from building muscle to improving explosive power.
What is a One Rep Max (1RM)?
Your one rep max is the maximum amount of weight you can lift for a single repetition of an exercise with proper form. This number is crucial for properly structuring your training program because many workout routines are based on percentages of your 1RM. Rather than testing your actual 1RM (which can be risky), you can estimate it by entering a weight you can lift for multiple reps into our calculator.
How to Use This Calculator
- Step 1: Choose whether you're calculating for an upper body (e.g., bench press) or lower body (e.g., squat, deadlift) exercise
- Step 2: Enter the weight you can lift with proper form for 4-6 reps
- Step 3: Enter the number of reps you can complete with this weight
- Step 4: Click calculate to see your estimated 1RM and training percentages
- Step 5: Use the training percentages table to select weights based on your goals
Understanding Training Percentages
Different training goals require different percentages of your 1RM:
50% 1RM: Best for explosive power and speed training. Use fast, explosive movements with this lighter weight.
70% 1RM: Ideal for muscular endurance and conditioning. This moderate weight allows high rep ranges.
80% 1RM: The sweet spot for muscle growth (hypertrophy). This weight allows enough reps while maintaining tension.
90% 1RM: Used for developing maximum power. Focus on moving these heavy weights as explosively as possible.
95% 1RM: Pure strength training. These near-maximal weights require perfect form and should be used sparingly.
Formula & Accuracy
This calculator uses formulas developed by the University of New Mexico, which are among the most accurate for estimating 1RM. The upper body formula is (weight × 1.1307) + 0.6998, while the lower body formula is (weight × 1.09703) + 14.2546. These equations are most accurate when using a weight you can lift for 4-6 reps. Accuracy decreases with higher rep ranges.
How to Use
- Select your exercise type (upper or lower body)
- Enter the weight you can lift for multiple reps
- Input the number of reps you can perform with good form
- Click calculate to see your estimated one rep max
- Review the training percentages for different goals
- Use the recommended weights in your training program
Watch Out For
- Using poor form when testing your working weight
- Testing 1RM with too many reps (accuracy decreases above 6 reps)
- Not warming up properly before maximal lifting
- Trying to test true 1RM without proper preparation
- Using inaccurate or estimated weights
- Not accounting for fatigue when testing
FAQs
How accurate is a 1RM calculator?
1RM calculators are most accurate when using weights you can lift for 4-6 reps with good form. Accuracy decreases with higher rep ranges.
Should beginners test their 1RM?
Beginners should use this calculator rather than testing true 1RM, which can be risky without proper experience and form.
How often should I recalculate my 1RM?
Test and recalculate every 4-6 weeks of consistent training, or whenever you feel significantly stronger.
Why do I need to know my 1RM?
Your 1RM helps structure training programs by letting you calculate exact weights for different goals like strength, power, or muscle growth.