Formulas
| Formula | Equation |
|---|---|
| Epley | weight × (1 + reps ÷ 30) |
| Brzycki | weight × 36 ÷ (37 − reps) |
| Lombardi | weight × reps0.10 |
We show the average of all three. Estimates are most reliable for sets of 10 reps or fewer.
Using your 1RM
- Strength: 80–90% of 1RM for 3–6 reps.
- Muscle growth: 65–80% of 1RM for 8–12 reps.
- Endurance: below 65% for 15+ reps.
Frequently asked questions
Is it safe to test a real 1RM?
Only with experience, a proper warm-up and a spotter. Estimating from 3–8 reps is safer for most people.
Which 1RM formula is best?
Epley and Brzycki are the most common. They agree closely for 2–10 reps.
Sources
- Epley B (1985); Brzycki M (1993); Lombardi VP (1989). One-repetition maximum prediction equations.
Medical disclaimer: This calculator gives estimates for general information only. It is not a diagnosis or a substitute for advice from a doctor or registered dietitian. Please consult a healthcare professional before making changes to your diet, exercise or medicines, especially if you are pregnant, have a medical condition or take regular medication.
Last updated: 20 October 2026. Read our editorial policy.
