1RM calculator: Epley, Brzycki, Lombardi

The 1RM (one-rep max) is your maximum load on a single clean rep. It is the gold standard for driving intensity in strength and powerlifting: most programs prescribe loads as a percentage of 1RM.

Rather than testing 1RM cold (risky), you can estimate it from a heavy set taken to near-failure. The calculator offers the three most-used formulas and their average.

The three formulas

• Epley: 1RM = load × (1 + reps / 30). Simplest, reliable up to 10 reps.
• Brzycki: 1RM = load × 36 / (37 - reps). Accurate on 1-10 reps, underestimates above.
• Lombardi: 1RM = load × reps^0.10. More conservative, useful for hypertrophy.
• Average: averaging the three smooths individual biases. Recommended default.

Accuracy and limits

Formulas are reliable up to 10 reps. Beyond (15+ reps), they drift: cardio fatigue takes over from pure strength. For high reps, estimated 1RM is indicative, not a target to test.

Using your 1RM in programming

The %1RM table maps a percentage of 1RM to a target rep count. Classic references:

• 95-100%: 1-2 reps. Max strength, peaking.
• 85-90%: 3-5 reps. Pure strength, base.
• 75-85%: 5-8 reps. Strength-hypertrophy.
• 65-75%: 8-12 reps. Pure hypertrophy.
• 50-65%: 12-20 reps. Muscular endurance, metabolic.

Programming 1RM in Unbrokn

In Unbrokn for strength and powerlifting, you write blocks in %1RM. Each athlete logs their 1RM in their space: when you program "5×3 @ 85% Squat", everyone sees their load auto-computed from their PR.

FAQ

Should I test my real 1RM?

Not in routine. Estimates from heavy sets (3-5 reps) are enough to program. Real test useful at peak or before competition.

Which formula to pick?

The average is the safest default. Low reps (1-5): Brzycki. Higher (8-12): Epley.