💪 🏋️ 💪
One Rep Max Calculator
Calculate your maximum strength using multiple estimation formulas. Estimate your 1RM safely from submaximal weights without directly testing your max.
📋 Quick Navigation
🏋️ Enter your weight and reps to calculate your estimated 1RM! 💪
Weight in kg or lbs
Number of reps completed
Average Estimated One Rep Max
0
Based on 100 × 5 reps
Weight Lifted
100
kg / lbs
Reps Performed
5
repetitions
Percentage of 1RM
87%
estimated
Epley Formula
0
Most popular & reliable for 1-10 reps
Brzycki Formula
0
Best for lower reps (3-8 range)
Lombardi Formula
0
Good for higher rep ranges
O'Conner Formula
0
Conservative for higher reps
🧮 One Rep Max Formulas
Epley Formula
The most popular formula, works well across various rep ranges. Developed based on observation of actual lifting performance.
1RM = Weight × (1 + 0.0333 × Reps)
Example: 100 kg × 5 reps
1RM = 100 × (1 + 0.0333 × 5)
1RM = 100 × (1 + 0.1665)
1RM = 100 × 1.1665
1RM ≈ 116.65 kg
Example: 100 kg × 5 reps
1RM = 100 × (1 + 0.0333 × 5)
1RM = 100 × (1 + 0.1665)
1RM = 100 × 1.1665
1RM ≈ 116.65 kg
Brzycki Formula
Considered most accurate for lower rep ranges (3-8 reps). Based on extensive empirical data from strength athletes.
1RM = Weight ÷ (1.0278 − 0.0278 × Reps)
Example: 100 kg × 5 reps
1RM = 100 ÷ (1.0278 − 0.0278 × 5)
1RM = 100 ÷ (1.0278 − 0.139)
1RM = 100 ÷ 0.8888
1RM ≈ 112.5 kg
Example: 100 kg × 5 reps
1RM = 100 ÷ (1.0278 − 0.0278 × 5)
1RM = 100 ÷ (1.0278 − 0.139)
1RM = 100 ÷ 0.8888
1RM ≈ 112.5 kg
Lombardi Formula
Uses an exponential calculation. Works better for higher rep ranges (8+ reps) and accounts for endurance factor.
1RM = Weight × (Reps)^0.10
Example: 100 kg × 5 reps
1RM = 100 × (5)^0.10
1RM = 100 × 1.1746
1RM ≈ 117.46 kg
Example: 100 kg × 5 reps
1RM = 100 × (5)^0.10
1RM = 100 × 1.1746
1RM ≈ 117.46 kg
O'Conner Formula
Conservative formula that performs well for higher rep ranges. Provides more realistic estimates when doing 10+ reps.
1RM = Weight × (1 + 0.025 × Reps)
Example: 100 kg × 5 reps
1RM = 100 × (1 + 0.025 × 5)
1RM = 100 × (1 + 0.125)
1RM = 100 × 1.125
1RM ≈ 112.5 kg
Example: 100 kg × 5 reps
1RM = 100 × (1 + 0.025 × 5)
1RM = 100 × (1 + 0.125)
1RM = 100 × 1.125
1RM ≈ 112.5 kg
📊 Formula Accuracy & Comparison
When to Use Each Formula
Different formulas are optimized for different rep ranges. Choosing the right formula for your rep range increases accuracy:
| Rep Range | Best Formula | Why | Accuracy |
|---|---|---|---|
| 1-2 reps | Brzycki | Optimized for low reps | ±5% |
| 3-8 reps | Brzycki or Epley | Both perform well in this range | ±7-10% |
| 8-10 reps | Epley | Good balance across ranges | ±10-12% |
| 10-15 reps | Lombardi or O'Conner | Account for endurance factor | ±10-15% |
| 15+ reps | Lombardi | Better for very high reps | ±15-20% |
Why Estimates Vary
Different formulas give different results because they're based on different research populations and assumptions:
- Brzycki: Based on trained powerlifters and strength athletes
- Epley: Derived from general population fitness data
- Lombardi: Uses exponential scaling for endurance
- O'Conner: Conservative estimate for safety
💡 Best Practice: Use multiple formulas and average the results for a more accurate estimate. Aim for consistency in testing conditions (same exercise, same form, same time of day) for better tracking over time.
Factors Affecting Accuracy
Several factors can impact how accurate your 1RM estimate actually is:
- Exercise Type: Estimates are more accurate for compound lifts (squat, bench, deadlift)
- Training Experience: More accurate for trained lifters than beginners
- Rep Range: More accurate closer to 10 reps
- Form Quality: Must maintain strict form for valid estimate
- Individual Variation: Some people's max strength doesn't correlate perfectly to rep performance
💪 Training Percentages of 1RM
Standard Training Zones
Once you know your 1RM, you can calculate training weights for specific rep ranges and goals:
| Training Zone | % of 1RM | Rep Range | Goal |
|---|---|---|---|
| Endurance | 50-70% | 12-20+ reps | Muscular endurance, volume |
| Hypertrophy | 70-85% | 6-12 reps | Muscle growth, size |
| Strength | 85-95% | 1-6 reps | Maximum strength |
| Power | 75-90% | 1-5 reps (explosive) | Speed and explosiveness |
Percentage of 1RM by Reps
Approximate percentage of 1RM for different rep maximums:
| Reps | % of 1RM (Approx) | Training Purpose |
|---|---|---|
| 1 | 100% | Maximum strength test |
| 3 | 93% | Heavy compound work |
| 5 | 87% | Strength building |
| 8 | 80% | Hypertrophy focus |
| 10 | 75% | Mixed volume work |
| 15 | 65% | Endurance training |
| 20 | 50-60% | Light endurance |
💡 Tip: These are general guidelines. Your actual percentages may vary slightly based on exercise selection, training history, and individual factors. Use these as starting points and adjust based on actual performance!
❓ Frequently Asked Questions
Is estimating 1RM safer than directly testing it?
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Yes! Directly testing your 1RM carries significant injury risk, especially for inexperienced lifters. Estimating from submaximal weights (2-10 reps) is much safer because you don't put your body under dangerous maximum load conditions. The formulas are surprisingly accurate when used properly. Always warm up thoroughly before any maximum effort work!
Which rep range is best for accurate 1RM estimation?
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The 5-10 rep range provides the best estimates. If you can do 5-6 reps with a weight, Brzycki formula is excellent. For 8-10 reps, Epley is very accurate. For higher reps (15+), Lombardi works better. Avoid testing beyond 15 reps as estimates become less accurate due to metabolic factors.
Why do different formulas give different results?
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Each formula was developed using different research populations (strength athletes vs general population) and has different assumptions about how strength relates to reps. Brzycki emphasizes strength athletes, Epley uses broader data, Lombardi accounts for endurance. That's why averaging multiple formulas gives better results than relying on one!
How do I use my 1RM for training?
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Your 1RM is the reference point for calculating training weights. Multiply your 1RM by the percentage for your goal: 85-95% for strength (1-6 reps), 70-85% for hypertrophy (6-12 reps), 50-70% for endurance (12+ reps). Update your 1RM estimate every 4-6 weeks as you get stronger!
Can I test 1RM on any exercise?
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Yes, but estimates are most accurate for compound lifts (squat, bench press, deadlift). For isolation exercises, direct testing might be necessary for accuracy. Also, technique matters a lot - maintain perfect form throughout your test set or the estimate won't be valid!
Should I warm up before testing?
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Absolutely! Proper warm-up is essential: 5-10 minutes light cardio, dynamic stretching, then progressively heavier sets (50%, 70%, 85% of your test weight). Good warm-up improves performance, prevents injury, and makes your test more accurate. Don't skip warm-up!
How often should I recalculate my 1RM?
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Recalculate every 4-6 weeks during training cycles to track progress and adjust training weights. More frequent testing (weekly) adds fatigue without benefit. Less frequent (every 8-12 weeks) means your training weights become outdated. Every month is a good balance!
What if my estimate seems way off?
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Several reasons: poor form during testing, not going to actual failure, equipment variation, or individual response differences. Average multiple formulas rather than using just one. If estimates consistently seem high, adjust down 10% for safety. Track actual lifts to compare!