How the 1RM Calculator works
Four validated formulas are averaged to give the most reliable estimate:
| Formula | Equation | Best for |
|---|---|---|
| Epley (1985) | w × (1 + r/30) | General use, most common |
| Brzycki (1993) | w × 36/(37−r) | Lower rep ranges (1–10) |
| Lander | w × 100/(101.3−2.67×r) | Higher rep ranges |
| O'Conner | w × (1 + 0.025×r) | Conservative estimate |
Accuracy decreases with higher reps (15+). Best results with 2–8 rep sets.
How to use your results
Use your 1RM to set training weights for different goals:
- Strength (1–5 reps): 85–100% 1RM
- Hypertrophy (6–12 reps): 67–85% 1RM
- Muscular endurance (12–20 reps): 50–67% 1RM
Test your 1RM with caution: warm up thoroughly, use a spotter, and only attempt true maximal lifts after 6+ months of consistent training.
Frequently asked questions
What is a one rep max (1RM)?
A one rep max (1RM) is the maximum weight you can lift for exactly one repetition with proper form. It's the standard measure of strength in powerlifting and weightlifting.
How accurate is the 1RM calculator?
The calculator is accurate to within 5–10% for most people using 2–8 rep sets. Accuracy decreases with higher reps (12+) and varies by exercise and training style.
Is it safe to test my actual 1RM?
Testing an actual 1RM is safe for experienced lifters with good technique and a spotter. Beginners should estimate from the calculator using a comfortable 5–8 rep set rather than attempting true maximal lifts.
How often should I test my 1RM?
Every 4–8 weeks is a reasonable frequency for experienced lifters. More frequent testing doesn't improve strength and increases injury risk. Many programs test 1RM every training cycle (8–16 weeks).
What percentage of my 1RM should I train at?
Hypertrophy (muscle growth): 70–85% for 6–12 reps. Strength: 85–95% for 1–5 reps. Power: 60–80% for explosive sets. General fitness: 60–75% for 10–15 reps.
How quickly can I increase my 1RM?
Beginners may see 5–10% monthly increases. Intermediate lifters: 2–5% monthly. Advanced: 1–2% monthly or less. Strength gains are slower but more permanent than early beginner progress.
Does body weight affect 1RM?
Yes — heavier people generally lift more in absolute terms but not necessarily relative to body weight. Strength-to-weight ratio (1RM / body weight) is used for comparing across weight classes.
What is a good 1RM for bench press?
For untrained men: bodyweight (×1.0). Intermediate: ×1.25. Advanced: ×1.5+. Elite: ×2.0+. For women: untrained ×0.55, intermediate ×0.75, advanced ×1.0+. Standards vary significantly by age and training history.