Disclaimer: This calculator provides *estimates* based on common formulas (like 220-Age for Max HR). Actual Maximum Heart Rate can vary significantly between individuals. The Karvonen formula using Resting Heart Rate provides a potentially more personalized estimate but still relies on an estimated Max HR. These zones are general guidelines. Factors like medication, fitness level, temperature, and health conditions can affect heart rate. Always consult with a doctor before beginning or modifying an exercise program. Listen to your body and adjust intensity based on how you feel (Rate of Perceived Exertion).