The Holy Grail of Strength

Your One Rep Max (1RM) is the theoretical maximum weight you can lift for a single repetition with proper form. It is the baseline metric for almost all periodized strength programs (Wendler 5/3/1, Juggernaut, Sheiko).

📐 The Math: Epley Formula

This calculator uses the Epley Formula (1985), widely considered the most accurate for general lifting populations: * Formula: 1RM = Weight * (1 + Reps / 30) * Accuracy**: Most accurate in the **3-6 rep range. * Limitation: As reps increase (>10), accuracy decreases because cardiovascular fatigue becomes a limiting factor before muscular failure.

🛡️ Why Estimate instead of Test?

Testing a true 1RM is taxing on the Central Nervous System (CNS) and carries a high injury risk. * CNS Fatigue: A true max effort can take 10-14 days to fully recover from. * Form Breakdown: Under maximal load, technique often degrades. * Recommendation: Test your 3RM or 5RM and use this calculator to find your training max.

🏋️ Training Zones by Percentage

| Goal | % of 1RM | Rep Range | Rest | | :--- | :--- | :--- | :--- | | Max Strength | 85-100% | 1-5 | 3-5 mins | | Hypertrophy (Size) | 70-85% | 6-12 | 1-2 mins | | Endurance | < 65% | 15+ | 30-60 secs | | Power (Speed) | 40-60% | 1-3 | 2-3 mins |

🧠 RPE (Rate of Perceived Exertion) Guide

If you don't know your max, use RPE to gauge intensity. * RPE 10: Max effort. No reps left in the tank. (Total Failure) * RPE 9: Heavy. Could do 1 more rep. * RPE 8: Hard. Could do 2 more reps. * RPE 7: Moderate speed. Could do 3 more reps.