🏋️ 1RM Calculator
Estimate your one-repetition maximum using the Brzycki formula
Your One-Rep Max Estimate:
Training Weight Recommendations:
ℹ️ About One-Rep Max
Your one-repetition maximum (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. Knowing your 1RM helps design effective strength training programs.
Step-by-Step Instructions:
- Select your preferred weight units (kg or lbs)
- Enter the weight you lifted
- Enter how many reps you completed with that weight (1-10)
- Click "Calculate 1RM"
Weight: 70 kg (154 lbs)
Reps: 5
Brzycki 1RM: ~80 kg (176 lbs)
Training Weight at 80%: ~64 kg (141 lbs) for 8-10 reps
Measurement Tips
- Test with a weight you can lift for 3-10 reps for safety
- Perform after proper warm-up but before fatigue sets in
- Use the same exercise form you'd use for max attempts
- For most accurate results, test multiple exercises separately
Brzycki Formula
The primary formula used in this calculator:
1RM = Weight × (36 / (37 - Reps))
Considered one of the most accurate formulas for reps ≤ 10.
Epley Formula
1RM = Weight × (1 + 0.0333 × Reps)
Simple formula that works well for moderate rep ranges.
Lombardi Formula
1RM = Weight × Reps^0.1
Better for power exercises like Olympic lifts.
Mayhew Formula
1RM = (100 × Weight) / (52.2 + (41.9 × e^(-0.055 × Reps)))
More complex but very accurate across rep ranges.
Which Formula is Best?
Brzycki is recommended for most strength exercises. Comparing multiple formulas gives you a range to work with. Actual 1RM testing is always most accurate but carries more risk.
Strength Training (90% of 1RM)
3-5 reps per set, 3-5 minutes rest between sets
Focus on maximal strength development
Hypertrophy Training (70-80% of 1RM)
8-12 reps per set, 1-2 minutes rest between sets
Ideal for muscle growth
Endurance Training (60% of 1RM)
15-20 reps per set, 30-60 seconds rest
Improves muscular endurance
Periodization
Use different percentages throughout your training cycle:
- Preparation Phase: 60-70% for higher volume
- Strength Phase: 80-90% for lower reps
- Peaking Phase: 90%+ for maximal strength
When to Avoid True 1RM Testing
- Beginners (train for at least 6 months first)
- Without proper warm-up
- Without spotters for barbell exercises
- When fatigued or recovering from injury
- For exercises with high injury risk (e.g., behind-the-neck press)
Safer Alternatives
- Use this calculator with submaximal weights
- Test with machines before free weights
- Use safety bars in power racks
- Consider using reps-to-failure with lighter weights
Exercise-Specific Notes
- Squat/Bench/Deadlift: Standard 1RM tests
- Overhead Press: More variance in technique
- Bodyweight Exercises: Add weight incrementally
- Unilateral Exercises: Test both sides
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