How accurate is the Brzycki formula for 1RM?

The Brzycki formula (1RM = weight / (1.0278 − 0.0278 × reps)) is most accurate for 1–10 reps. Accuracy decreases for higher reps (15+). For best results, use 3–8 rep sets. Other formulas (Epley, Lombardi) give similar results. All are estimates — actual 1RM requires a true max effort test.

How do I use 1RM for training?

Training percentages by goal: Strength: 85–95% of 1RM, 1–5 reps. Hypertrophy (muscle size): 65–85%, 6–12 reps. Muscular endurance: 50–65%, 12–20+ reps. Power: 30–60% at max speed. Most powerlifters train at 70–85% for most sessions and rarely go above 90%.