One Rep Max Calculator
Estimate your one-rep max (1RM) based on submaximal lifts. Get accurate training percentages and weight recommendations for strength programs.
Your one-rep max estimate and training percentages will appear here.
How to Use the One Rep Max Calculator
- Enter Weight: Input the weight you lifted (select lbs or kg)
- Enter Reps: Number of repetitions completed with good form
- Select Exercise (Optional): Choose your lift for context
- Choose Formula: Select calculation method (Epley is most common)
- Calculate: Get your estimated 1RM and training percentages
What is One-Rep Max (1RM)?
Your one-rep max is the maximum weight you can lift for a single repetition with proper form. It's a key metric in strength training used to:
- Track strength progress over time
- Design training programs with appropriate intensities
- Compare performance across different exercises and athletes
- Set realistic goals for competition or personal achievement
Understanding 1RM Formulas
Epley Formula (1952)
1RM = weight × (1 + reps/30)
Most widely used formula. Works well across all rep ranges. Example: 225 lbs × 5 reps = 225 × (1 + 5/30) = 262.5 lbs
Brzycki Formula (1993)
1RM = weight × (36 / (37 - reps))
Tends to be slightly more conservative. Popular in powerlifting circles.
When to Use Each Formula
| Formula | Best For | Characteristics |
|---|---|---|
| Epley | General use, all lifts | Balanced, most commonly used |
| Brzycki | Lower reps (1-5) | More conservative estimates |
| Average | Most accurate estimate | Averages all formulas |
Training Percentages Explained
Training programs prescribe intensity as a percentage of your 1RM. Here's what each range targets:
90-100% of 1RM
Rest: 3-5 minutes
Use: Powerlifting, peaking phase
80-90% of 1RM
Rest: 2-4 minutes
Use: Strength building phase
70-80% of 1RM
Rest: 60-90 seconds
Use: Bodybuilding, muscle gain
60-70% of 1RM
Rest: 30-60 seconds
Use: Conditioning, endurance sports
Frequently Asked Questions
How accurate are 1RM calculators?
1RM calculators are most accurate with 1-10 reps. The ideal testing range is 3-5 reps. Estimates become less reliable above 10 reps due to fatigue factors. Most formulas are accurate within ±5% when used in the optimal rep range.
Should I actually test my 1RM?
Testing true 1RM is risky and not necessary for most people. It requires perfect form, proper warm-up, and ideally a spotter. Using a calculator with 3-5 rep sets is safer and nearly as accurate. Reserve true 1RM testing for competition or under professional supervision.
Why do different formulas give different results?
Each formula was developed from different populations and lifting data. Some are more conservative (Brzycki), others more liberal (Lombardi). The differences are usually small (5-10 lbs). Using "Average of All" provides a balanced estimate.
How often should I recalculate my 1RM?
Recalculate every 4-6 weeks or whenever you notice significant strength gains. Your 1RM naturally increases with consistent training, so updating ensures your training percentages remain accurate.
What if I can do more than 10 reps?
The calculator works but becomes less accurate. If you're doing 10+ reps, increase the weight until you're in the 5-8 rep range, then recalculate. This gives more reliable 1RM estimates.
Can I use this for dumbbell exercises?
Yes, but enter the total weight. If using 50 lb dumbbells, enter 100 lbs. Note that dumbbell 1RM is typically lower than barbell equivalents due to stability demands.
How do I use 1RM percentages in my program?
Most programs specify "3 sets of 5 reps at 80% 1RM" or similar. Calculate your 1RM, then multiply by the percentage (e.g., 300 lbs × 0.80 = 240 lbs). The calculator provides these percentages automatically.
💪 1RM Testing Best Practices
- Proper Warm-Up: 5-10 min cardio, then progressive sets (40%, 60%, 80% of expected max)
- Rest Adequately: Take 3-5 minutes rest before attempting heavy sets
- Use Spotters: Always have spotters for bench press and squats
- Maintain Form: Stop if form breaks down - a 1RM with bad form doesn't count
- Test When Fresh: Avoid testing after hard training; be well-rested
- Progressive Approach: Increase weight in small increments (5-10 lbs)
Improving Your 1RM
Periodization: Cycle through hypertrophy (8-12 reps), strength (3-6 reps), and power (1-3 reps) phases. This builds muscle, then converts it to strength.
Progressive Overload: Increase weight by 2.5-5 lbs per week on major lifts. Small, consistent gains compound over time.
Recovery Matters: Strength gains happen during recovery. Ensure 48+ hours between heavy sessions for the same muscle groups, prioritize 7-9 hours of sleep, and maintain adequate protein intake (0.7-1g per lb bodyweight).
1RM estimates are approximations and should not replace proper strength testing under supervision. Always use proper form, adequate warm-up, and spotters when lifting heavy weights. Consult a qualified trainer or coach before attempting maximum lifts.