One Rep Max (1RM) Calculator
About 1RM
What is 1RM?
Your one-rep max is the maximum weight you can lift for a single repetition with proper form.
Most Accurate
Estimates are most accurate with 1-10 reps. Higher reps increase error margin.
Safety First
Always use a spotter or safety bars when testing true 1RM. Estimating is safer!
Common Lifts
Related Calculators
Understanding One Rep Max
What Is 1RM?
Your one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a key metric in strength training used to program workouts, track progress, and compare relative strength across different exercises.
Why Estimate Instead of Test?
Testing a true 1RM is risky and requires proper preparation, spotters, and recovery time. Estimating from submaximal lifts is safer and can be done more frequently to track progress.
Popular 1RM Formulas
| Formula | Equation | Best For |
|---|---|---|
| Brzycki | w / (1.0278 - 0.0278r) | 1-10 reps |
| Epley | w × (1 + r/30) | General use |
| Lander | 100w / (101.3 - 2.67r) | 1-10 reps |
| Lombardi | w × r^0.1 | Higher reps |
| Mayhew | 100w / (52.2 + 41.9e^-0.055r) | Research-based |
| O'Conner | w × (1 + r/40) | Conservative |
Training Zones by Percentage
Strength (85-100%)
1-5 reps. Maximum strength development. Requires longer rest periods (3-5 min) and careful programming to avoid overtraining.
Hypertrophy (65-85%)
6-12 reps. Optimal for muscle growth. Moderate rest (60-90 sec) between sets.
Endurance (50-65%)
15-20+ reps. Muscular endurance and conditioning. Short rest periods (30-60 sec).
Power (30-60%)
Explosive movements at lower percentages. Focus on speed of movement rather than load.
How to Get Accurate Estimates
Use 3-8 Rep Range
Formulas are most accurate with lower reps. Sets of 3-8 reps give better estimates than 15-20 reps.
True Failure or RPE 10
The reps must be to failure or RPE 10 (no reps left in the tank) for accurate results.
Good Form Throughout
Only count reps performed with proper technique. Cheating reps don't count toward your estimate.
Strength Standards
These general strength standards for adult males are based on body weight ratios. Women's standards are typically 60-70% of these values. Individual results vary based on training experience, genetics, and body composition.
| Level | Bench | Squat | Deadlift |
|---|---|---|---|
| Beginner | 0.5× BW | 0.75× BW | 1× BW |
| Novice | 0.75× BW | 1× BW | 1.25× BW |
| Intermediate | 1× BW | 1.5× BW | 1.75× BW |
| Advanced | 1.5× BW | 2× BW | 2.5× BW |
| Elite | 2× BW | 2.5× BW | 3× BW |
Safety First
- Always warm up thoroughly before heavy lifting
- Use spotters or safety bars when testing heavy weights
- Progress gradually—don't jump to estimated maxes immediately
- If you haven't lifted in a while, start conservatively
- Listen to your body and stop if something feels wrong
Frequently Asked Questions
What is a one rep max (1RM)?
Your one rep max is the maximum amount of weight you can lift for a single repetition with proper form. It's used to gauge strength levels, compare lifts relative to body weight, and calculate training percentages for strength programs. Rather than testing true maxes regularly, most lifters estimate 1RM from submaximal sets.
How accurate are 1RM calculators?
1RM calculators are most accurate when using sets of 3-8 reps to failure. Accuracy decreases with higher rep ranges (10+). Most formulas are within 5-10% of actual max for trained lifters. Individual factors like training experience, muscle fiber composition, and exercise type affect accuracy. Use results as estimates.
What percentage of my 1RM should I train at?
Training percentages depend on your goal. For maximum strength, use 85-100% (1-5 reps). For muscle growth (hypertrophy), use 65-85% (6-12 reps). For muscular endurance, use 50-65% (15+ reps). Most programs vary percentages across different training blocks and exercises.
How often should I test or estimate my 1RM?
Retesting 1RM every 8-12 weeks is sufficient for most lifters. Testing true maxes is taxing and requires recovery time. Estimating from submaximal sets can be done more frequently - even weekly if needed. Track trends over time rather than obsessing over single tests, as daily performance varies.