The formulas
Epley: 1RM = w × (1 + r/30). Brzycki: 1RM = w × 36/(37 − r). For 185 lb × 5: Epley 215.8 lb, Brzycki 208.1 lb, average 212 lb. A single rep returns the weight itself.
Using your 1RM
Percentage-based programmes prescribe loads as a share of your max: for example 5 sets of 5 at 80–85%. Re-estimate every few weeks from a hard working set rather than maxing out. Warm up, keep good form, and stop a set if technique breaks down. If you have a heart condition, high blood pressure, or are pregnant, ask your clinician before heavy lifting.
Questions people ask
How do I calculate my one rep max?
Lift a weight you can handle for 3–8 good reps, then plug the weight and reps into a formula. Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). This calculator averages the two.
Is it safe to test a true 1RM?
Maximal lifts carry more risk, especially for beginners. Estimating from a submaximal set is safer and usually accurate enough to plan training. If you do test, use a spotter or safety bars and warm up thoroughly.
How accurate are 1RM calculators?
Within about 5% for most people when using 10 reps or fewer. Accuracy drops with higher reps and varies between exercises and individuals.
What percentage of 1RM should I train at?
Common guidance (NSCA) puts strength work at roughly 85% and above for up to 6 reps, muscle-building work around 67–85% for 6–12 reps, and muscular endurance below about 67% for 12+ reps.
Sources
- Epley B. (1985). Poundage chart. Boyd Epley Workout. University of Nebraska.
- Brzycki M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. JOPERD 64(1):88–90.
- NSCA. Essentials of Strength Training and Conditioning: %1RM–repetition relationship.
Every formula on VitalMetrics is listed with its original reference on Sources & methods.