One-Rep Max Calculator (1RM) with Training Percentages
Your one-rep max (1RM) is the heaviest weight you can lift once with good form. The BuyTheWhey 1RM calculator estimates it from a lighter set using the Epley and Brzycki formulas, so you don’t have to test a true max.
Free tool
One-Rep Max (1RM) Calculator
Your estimated max lift and training percentages.
Estimates for healthy adults, for general information only — not medical advice.
The formulas
- Epley: 1RM = weight × (1 + reps ÷ 30).
- Brzycki: 1RM = weight × 36 ÷ (37 − reps).
- The calculator shows the average of both, plus 60–95% training loads.
Frequently asked questions
How many reps give the most accurate 1RM estimate?
Sets of 3–10 reps give the most reliable estimates. Above about 10 reps, both formulas become less accurate.
What percentage of 1RM should I train at?
Roughly 67–85% of 1RM (about 6–12 reps) suits muscle growth, and 85% or more (1–5 reps) suits maximal strength.
These calculators give estimates for healthy adults and are for general information only. Speak to a doctor or registered dietitian before major diet changes.