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). Reliable up to 10 reps, applied up to 15.
• Brzycki: 1RM = load × 36 / (37 - reps). Accurate from 1 to 10 reps, not applied beyond.
• Lombardi: 1RM = load × reps^0.10. Highest estimate up to 5 reps, lowest from 8.
• Average: averaging the applicable formulas smooths their biases. It is the 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.

Accuracy also depends on when you do the set: cold underestimates, and so does a set done tired at the end of a session.

Using your 1RM in programming

The Berger table maps a percentage of 1RM to the maximum number of reps possible at that load. It is a guide, not a prescription: in training you usually stop 1 to 3 reps short.

• 95 to 100%: 1 to 2 max reps. Max strength.
• 85 to 90%: 4 to 6 max reps. Strength.
• 75 to 80%: 8 to 10 max reps. Strength and hypertrophy.
• 65 to 70%: 12 to 15 max reps. Hypertrophy.
• 50 to 60%: 18 to 25 max reps. Muscular endurance.

Programming 1RM in Unbrokn

In Unbrokn for strength and powerlifting, your coach inserts a "% of 1RM" reference in the exercise description (e.g. 85% of 1RM Back Squat). Each athlete sees their load computed from their own record. When they update it, loads follow. In the app, a record entered on 2 to 6 reps is converted to an estimated 1RM with Epley.

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.