Heart Rate Calculator
Calculate your maximum heart rate and personalized training zones using the Karvonen heart rate reserve formula.
How to use this heart rate calculator
- Enter your age — maximum heart rate declines approximately 1 bpm per year.
- Measure resting heart rate first thing in the morning before getting out of bed. Average 3 days for accuracy.
- Train in Zone 2 for aerobic base building and fat oxidation — most long-term fitness gains come here.
- Use Zone 4 intervals for cardiovascular fitness improvements.
- Zone 5 is sustainable only for short bursts — used in HIIT and racing, not sustained cardio.
Formula
Max HR = 220 − age. Karvonen zone = resting HR + (max HR − resting HR) × intensity. Heart rate reserve = max HR − resting HR.
About the Heart Rate Calculator
Heart rate training is the most practical tool for quantifying exercise intensity in real time without lab equipment. By exercising at specific heart rate zones, you can systematically target different physiological adaptations — fat oxidation, cardiovascular efficiency, speed, and power — rather than just exercising without a structured stimulus. The Karvonen formula, which this calculator uses, is more individualized than simpler percentage-of-maximum approaches. By incorporating resting heart rate, it accounts for the fact that a fit person with a 45 bpm resting heart rate and a sedentary person with a 75 bpm resting heart rate have very different heart rate reserves — their training zones should reflect this. The Karvonen formula uses heart rate reserve (HRmax − HRrest) as the scaling factor, producing zones that more accurately reflect physiological intensity. For health and longevity, the most impactful heart rate training zone is Zone 2. Research from multiple longitudinal studies shows that time spent in moderate aerobic activity is the strongest exercise predictor of long-term health outcomes — more predictive than high-intensity exercise volume. The American Heart Association's recommendation of 150 minutes of moderate aerobic activity per week corresponds roughly to Zone 2 training. For performance athletes, the distribution of training across zones matters enormously. Elite endurance athletes consistently show that top performers spend more training time in Zone 1–2 (easy) and Zone 4–5 (hard) than lower-performing peers, who tend to cluster in Zone 3. This counterintuitive finding — that elite performers train easier on most days — underlies the polarized training philosophy adopted by many high-performance coaches worldwide.
Frequently asked questions
+How accurate is the 220 minus age formula?
The 220 − age formula is a population average with substantial individual variation. The standard deviation is approximately 10–12 bpm — meaning 68% of people have true maximum heart rates within 10–12 bpm of the prediction, and roughly 5% are more than 20 bpm away. Some people in their 50s have maximum heart rates above 190 while others in their 20s top out at 175. For training purposes, zones calculated from the formula are approximate. The most accurate way to determine true maximum heart rate is a graded exercise test supervised by a fitness professional or sports medicine physician.
+What is Zone 2 training and why is it so popular?
Zone 2 training (60–70% of heart rate reserve, roughly 60–70% of VO2 max) is the sweet spot for aerobic base building — the foundation of long-term cardiovascular fitness. At Zone 2 intensity, the body primarily uses fat as fuel, trains mitochondrial density and efficiency, and can be sustained for extended periods without the recovery cost of higher intensity work. Research by physiologists like Iñigo San Millán has popularized Zone 2 with endurance athletes and health-focused individuals. Most recreational exercisers train too hard — consistently at Zone 3–4 intensity without enough Zone 2 base work, which limits long-term fitness development.
+What is resting heart rate and what does it indicate?
Resting heart rate (RHR) is heartbeats per minute when completely at rest — ideally measured first thing in the morning before rising. Normal range for adults is 60–100 bpm; athletes often have RHRs of 40–60 bpm. Lower resting heart rates in healthy adults generally indicate better cardiovascular fitness — a more efficient heart pumps more blood per beat, requiring fewer beats per minute at rest. Each 1 bpm reduction in resting heart rate from exercise training corresponds to approximately 0.5% reduction in cardiovascular disease mortality risk in population studies.
+How should I use heart rate zones in my workouts?
A well-structured training program typically follows an 80/20 distribution: approximately 80% of training time in Zone 1–2 (aerobic base) and 20% in Zone 4–5 (high intensity). This polarized training approach is supported by research across multiple endurance sports and produces better fitness gains than spending most time in Zone 3. In practice: easy days stay genuinely easy (conversational pace), and hard days involve true high-intensity intervals. The common mistake is grinding through Zone 3 — hard enough to be uncomfortable but not hard enough to drive adaptation, while accumulating fatigue that prevents quality hard sessions.
+What is the difference between aerobic and anaerobic exercise?
Aerobic exercise occurs when intensity is low enough that the cardiovascular system supplies adequate oxygen to working muscles, allowing sustained fat and carbohydrate oxidation. Zone 1–3 training is predominantly aerobic. Anaerobic exercise occurs when intensity exceeds the lactate threshold — muscles produce energy faster than oxygen can be delivered, resulting in lactic acid accumulation and rapid fatigue. Zone 4–5 is predominantly anaerobic. Both are valuable: aerobic training builds the base for cardiovascular health and long-duration performance. Anaerobic training improves power output, speed, and raises the lactate threshold.