One-Rep Max Calculator
Estimate your one-rep max and get percentage-based training weights without maximal testing.
What Is a One-Rep Max?
A one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It's a key metric used by strength athletes and coaches to measure strength, track progress, and design effective training programs.
Why Calculate Your 1RM?
- Provides a baseline measurement of your current strength
- Allows you to track progress over time
- Helps determine appropriate working weights for different training goals
- Enables more precise program design using percentage-based training
- Safer than attempting actual 1RM tests, especially for beginners
Safety Considerations
Testing your true one-rep max can be risky, especially for beginners or when performed without proper supervision. Our calculator provides a safe alternative by estimating your 1RM based on the weight you can lift for multiple repetitions.
If you do attempt a true 1RM test, always:
- Use proper form and technique
- Have an experienced spotter or coach present
- Use safety equipment (power rack, safety bars, etc.)
- Warm up thoroughly with progressively heavier weights
- Don't test 1RMs when fatigued or recovering from injury
Note: This calculator provides an estimate only. Your actual one-rep max may vary.
For safety, consider working with a spotter when testing your true one-rep max.
Understanding Percentage-Based Training
Maximum Strength (90-100%)
Training with weights at 90-100% of your 1RM develops maximum strength and neural adaptations.
Characteristics:
- Very heavy weights
- Low repetitions (1-3 reps)
- Longer rest periods (3-5 minutes)
- Focus on neural efficiency
- Best for strength athletes and advanced lifters
Strength/Power (80-90%)
Training in this range builds strength while still allowing for good technique and moderate volume.
Characteristics:
- Heavy weights
- Low to moderate repetitions (3-6 reps)
- Substantial rest periods (2-3 minutes)
- Develops both strength and some muscle size
- Good for strength-focused training phases
Hypertrophy (65-80%)
This range is optimal for building muscle size (hypertrophy) while still using challenging weights.
Characteristics:
- Moderate weights
- Moderate repetitions (8-12 reps)
- Moderate rest periods (1-2 minutes)
- Maximizes muscle growth stimulus
- Ideal for bodybuilding and physique development
Muscular Endurance (50-65%)
Lower percentages with higher repetitions improve muscular endurance and work capacity.
Characteristics:
- Lighter weights
- Higher repetitions (12-20+ reps)
- Shorter rest periods (30-90 seconds)
- Improves muscular endurance and work capacity
- Good for conditioning phases and beginners
Deload/Recovery (40-50%)
Using lighter weights periodically allows for active recovery while maintaining movement patterns.
Characteristics:
- Light weights
- Moderate repetitions (8-15 reps)
- Focus on perfect technique
- Reduces fatigue while maintaining practice
- Important for long-term progress and injury prevention
Program Design Tips
How to effectively use percentage-based training in your workout routine.
Recommendations:
- Vary percentages throughout your training cycle
- Include different rep ranges for balanced development
- Periodically retest your 1RM (every 8-12 weeks)
- Start with lower percentages and gradually increase
- Include deload weeks with reduced percentages
About Our Calculator
Our One-Rep Max Calculator uses three scientifically validated formulas to estimate your maximum strength:
Brzycki Formula
1RM = weight × (36 / (37 - reps))
Most accurate for repetitions under 10. Our default and recommended formula.
Epley Formula
1RM = weight × (1 + 0.0333 × reps)
Works well across a wide range of repetitions. Simple and reliable.
Lander Formula
1RM = (100 × weight) / (101.3 - 2.67123 × reps)
Provides good accuracy, especially in the 5-10 rep range.
Ready to optimize your strength training?
Use our calculator to determine your one-rep max and get personalized training weights for your specific goals.
