1RM Calculator
Enter your lift to estimate your one rep max across three proven formulas
Enter a weight and reps to see your max
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What Is a One Rep Max (1RM)?
Your one rep max (1RM) is the heaviest weight you can lift for a single repetition with proper form. It is the gold standard for measuring maximal strength and is used by coaches, athletes, and researchers to prescribe training loads as a percentage of your max.
Rather than testing a true 1RM in the gym (which carries injury risk and requires peak readiness), you can estimate it from any set of submaximal reps using well-validated formulas.
The Formulas Behind This Calculator
- Brzycki formula — 1RM = weight × 36 / (37 − reps). Most accurate for 1-10 reps and the standard used by the NSCA.
- Epley formula — 1RM = weight × (1 + reps / 30). Widely used in research and most online calculators.
- Lombardi formula — 1RM = weight × reps^0.1. Provides a useful cross-check, especially at moderate rep ranges.
For the best estimate, enter a weight you lifted for 3-5 reps where the last rep was near failure. The three formulas converge most closely in this range. Above 10 reps, fatigue and technique become larger factors and accuracy drops.
NSCA Training Load Chart
The National Strength and Conditioning Association (NSCA) publishes a well-validated chart linking rep ranges to percentages of 1RM. This calculator generates a personalised training load chart so you know exactly how much weight to use for any target rep range:
- 1-3 reps (90-100% 1RM) — maximal strength and neural adaptations
- 4-6 reps (80-90% 1RM) — strength and power development
- 6-8 reps (75-85% 1RM) — strength-hypertrophy balance
- 8-12 reps (65-80% 1RM) — hypertrophy (muscle growth) zone
Strength Benchmarks by Bodyweight
Where does your lift rank? These general standards are based on competitive strength data and apply to adult male lifters. Female standards are roughly 60-70% of these values.
| Level | Bench Press | Squat | Deadlift |
|---|---|---|---|
| Beginner | 0.5× BW | 0.75× BW | 1× BW |
| Intermediate | 1× BW | 1.25× BW | 1.5× BW |
| Advanced | 1.5× BW | 2× BW | 2.5× BW |
| Elite | 2× BW | 2.5× BW | 3× BW |
BW = bodyweight. Standards based on drug-free male lifters. Adjust female standards to roughly 60-70% of these values.
How to Safely Test Your 1RM
- Only test when you have at least 6 months of consistent training and solid technique.
- Warm up thoroughly: 5-10 min general warm-up, then progressive sets at 50%, 70%, 85%, and 90% of your estimated max.
- Use a spotter or safety bars/pins. Never test alone.
- Take 3-5 minutes rest between heavy attempts.
- Stop if your form breaks down. A grind-it-out rep with bad form does not count and risks injury.
Frequently Asked Questions
How accurate are 1RM calculator formulas?
The Brzycki and Epley formulas are accurate to within 5% for sets of 1-10 reps. Accuracy decreases above 10 reps because fatigue and technique become larger variables. For the most reliable estimate, use a weight you can lift for 3-5 reps.
When should I test my actual one rep max?
Test a true 1RM only when you have at least 6 months of consistent training, proper technique, and ideally a spotter or safety equipment. Most lifters benefit more from estimating their 1RM from submaximal sets and training with percentages.
What is a good bench press for my bodyweight?
For men, a bodyweight bench press (1× BW) is considered intermediate, 1.5× BW is advanced, and 2× BW is elite. For women, 0.65× BW is intermediate, 1× BW is advanced, and 1.25× BW is elite. These standards vary by age and training background.
Which 1RM formula should I use?
Use the Brzycki formula for low-rep sets (1-6 reps) and the Epley formula for moderate rep ranges (6-10 reps). This calculator shows all three formulas so you can compare and take the average for the most reliable estimate.
How often should I recalculate my 1RM?
Recalculate every 4-8 weeks or whenever you complete a training cycle. As you get stronger your 1RM increases, so training percentages need updating to continue making progress.
How accurate is a 1RM calculator?
Most 1RM calculators are accurate to within 5% when using sets of 3-5 reps near failure. Accuracy decreases with higher rep sets (above 10) because fatigue, cardiovascular fitness, and technique play a larger role. For the best estimate, enter a recent set where the last rep was genuinely hard.
Should I test my 1RM or estimate it?
For most lifters, estimating is safer and more practical. True 1RM testing requires peak readiness, a spotter, and carries injury risk. Estimating from a 3-5 rep set gives you a reliable working number for programming without the recovery cost of a max-out session.
How often should I test my one rep max?
Only test a true 1RM every 12-16 weeks — typically at the end of a training block or before a competition. More frequent testing adds fatigue without much benefit. Between tests, use the calculator to estimate your 1RM from submaximal sets and adjust your training percentages accordingly.
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