1RM Calculator
Estimate your one-rep max from any weight and rep combination. Uses three proven formulas for accurate results.
Calculate Your 1RM
Enter your weight and reps above to calculate your estimated 1RM
For best accuracy, use a weight you can lift for 3-10 reps
About 1RM Formulas
Epley Formula: Most accurate for lower rep ranges (1-6 reps). Commonly used in strength training.
Brzycki Formula: More conservative estimates. Better for higher rep ranges (6-12 reps).
Lander Formula: Middle ground between Epley and Brzycki. Good all-around accuracy.
Note: These are estimates. Your actual 1RM may vary based on factors like fatigue, technique, and training experience. Always use a spotter when testing maxes.
Related Tools
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Arvo estimates your 1RM for every exercise automatically and shows progression over time.
- Automatic 1RM tracking
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- AI-powered load suggestions
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Dive deeper into strength training science with our comprehensive guides.
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What is a One Rep Max (1RM)?
Your one rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's the gold standard for measuring absolute strength and serves as the foundation for percentage-based training programs.
Knowing your 1RM allows you to calculate training loads precisely. Instead of guessing weights, you can train at specific intensities (like 80% of 1RM for strength or 70% for hypertrophy) that are proven to produce specific adaptations.
How 1RM is Calculated
There's no single "perfect" formula for estimating 1RM. Our calculator uses three established formulas, each with different strengths:
Epley Formula
1RM = Weight × (1 + Reps/30)Most accurate for low rep ranges (1-6). Widely used in powerlifting circles. Tends to slightly overestimate for higher reps.
Brzycki Formula
1RM = Weight × (36 / (37 - Reps))More conservative for higher rep ranges (6-12). Often preferred for general strength training. Produces lower estimates than Epley.
Lander Formula
1RM = (100 × Weight) / (101.3 - 2.67 × Reps)Good middle ground between Epley and Brzycki. Works well across rep ranges. Popular in academic research.
For best accuracy, use a weight you can lift for 3-10 reps. Above 10 reps, all formulas become significantly less accurate.
Using 1RM for Training Programming
Once you know your 1RM, you can program training with precise intensities:
| %1RM | Reps | Goal | Description |
|---|---|---|---|
| 90-100% | 1-3 reps | Maximum Strength | Peak strength and neural adaptations. High CNS fatigue, requires full recovery. |
| 80-90% | 3-6 reps | Strength | Primary strength building zone. Heavy enough for strength gains, enough reps for technique practice. |
| 70-80% | 6-12 reps | Hypertrophy | Optimal for muscle growth. Balances mechanical tension and metabolic stress. |
| 60-70% | 12-20 reps | Muscular Endurance | Builds work capacity and muscular endurance. Lower injury risk, good for beginners. |
| 50-60% | 20+ reps | Warm-up / Technique | Warm-up sets, technique work, or active recovery. Minimal strength stimulus. |
When to Test vs Estimate Your 1RM
Actually Testing Your 1RM
Pros:
- +Most accurate measurement
- +Builds confidence with heavy weights
- +Required for powerlifting competitions
- +Validates your training progress
Cons:
- −High injury risk if technique breaks down
- −Requires significant recovery time (5-7 days)
- −Needs proper warm-up and spotters
- −Taxes central nervous system heavily
Estimating with a Calculator
Pros:
- +Safe — no injury risk
- +Can do frequently without recovery cost
- +Works with any rep range
- +Good for tracking progress week-to-week
Cons:
- −Accuracy decreases above 10 reps
- −Doesn't account for psychological factors
- −Individual variation affects accuracy
- −Different exercises have different accuracy
For most lifters, estimate your 1RM using calculators and only test true maxes every 8-12 weeks or before competitions.
1RM Accuracy by Exercise Type
Not all exercises translate equally well to 1RM estimates:
| Type | Examples | Accuracy | Notes |
|---|---|---|---|
| Compound Barbell Lifts | Squat, Bench, Deadlift, OHP | High | Most accurate — these are what formulas were designed for |
| Compound Dumbbell Lifts | DB Bench, DB Rows, DB Lunges | Moderate | Stability demands may limit true max differently than higher reps |
| Machine Exercises | Leg Press, Chest Press, Lat Pulldown | Moderate | Fixed path reduces validity but estimates still useful |
| Isolation Exercises | Bicep Curls, Leg Extensions, Flyes | Low | 1RM testing not recommended — joint stress too high for benefit |
Common 1RM Myths Debunked
❌ You must test your 1RM regularly
✅ Estimating with formulas is safer and sufficient for training programming. True 1RM testing is taxing and carries injury risk. Test only every 8-12 weeks or before competitions.
❌ The true 1RM is always higher than estimates
✅ Formulas are accurate within 5-10% for most people. Your estimated 1RM may be close to or even slightly above your actual max depending on technique and experience.
❌ You need a 1RM for every exercise
✅ 1RM is mainly useful for the big compound lifts (squat, bench, deadlift). For isolation exercises, testing max is risky and unnecessary - use higher reps instead.
❌ A failed 1RM attempt means you're weak
✅ Many factors affect single-rep performance: sleep, stress, nutrition, warm-up, and psychological state. A bad day doesn't reflect your true strength.
❌ Your 1RM doesn't change quickly
✅ With specific training, your 1RM can improve week to week, especially in beginners and intermediates. Neural adaptations happen faster than muscle growth.
Frequently Asked Questions
What is a 1RM (one rep max)?
A 1RM is the maximum weight you can lift for a single repetition with proper form. It's used to measure strength progress and calculate training loads as percentages.
How do I calculate my 1RM?
To calculate your 1RM: (1) Enter a weight you can lift for multiple reps, (2) Enter the number of reps you completed with good form, (3) Our calculator applies proven formulas (Epley, Brzycki, Lander) to estimate your one rep max. For best accuracy, use a weight you can lift for 3-10 reps.
How accurate are 1RM calculators?
1RM calculators are most accurate for rep ranges of 1-10. Accuracy decreases with higher reps (10+). They provide estimates; your actual 1RM may vary based on fatigue, technique, and experience.
Which 1RM formula is best?
For low reps (1-6), the Epley formula is most accurate. For higher reps (6-12), Brzycki tends to be more conservative and realistic. We show all three formulas so you can compare.
How often should I test my 1RM?
Testing true 1RMs is taxing on your body. Most lifters test every 8-12 weeks. Using calculators between tests is safer and gives you training guidance without the recovery cost.
What percentage of 1RM should I train at?
For strength: 80-90% (3-6 reps). For hypertrophy: 65-80% (6-12 reps). For endurance: 50-65% (12+ reps). Most programs periodize across these ranges.
Track Your Strength Automatically
This calculator gives you a snapshot. Arvo tracks your estimated 1RM for every exercise, shows progression over time, and automatically adjusts your training loads based on performance.
Try Arvo FreeDisclaimer: This calculator provides estimates based on scientifically validated formulas (Epley, Brzycki, Lander). Results are most accurate for 1-10 rep ranges. Your actual 1RM may vary based on fatigue, technique, experience, and day-to-day condition. Testing true 1RM carries injury risk — use proper spotters and assess your experience level. Consult a qualified fitness professional for personalized guidance.