Heart Rate Zones Calculator
Find your 5 heart rate training zones using the Karvonen formula.
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Heart rate zones let you train at the right intensity for your specific fitness goals. This calculator uses the Karvonen formula, which accounts for your resting heart rate and provides more personalized zones than simple percentage-of-max formulas. Here is how to use it:
- Enter your age. If you do not know your actual max heart rate, the calculator estimates it as 220 minus your age, which is the most widely used formula.
- Enter your resting heart rate. Measure this first thing in the morning before getting out of bed. Count your pulse for 60 seconds or 30 seconds and multiply by two. The average for adults is 60-80 bpm, but trained endurance athletes often have resting rates below 50 bpm.
- Override max HR (optional). If you have done a max HR test (typically a hard interval or ramp test), enter your actual measured max for more accurate zones.
- Read your zones. Each zone shows the heart rate range and a description of its primary training benefit.
About Heart Rate Zones and the Karvonen Formula
The Karvonen formula calculates target heart rate as: Target HR = ((Max HR - Resting HR) × Intensity) + Resting HR. The difference between max and resting heart rate is called Heart Rate Reserve (HRR). The Karvonen method uses HRR so that the zones scale relative to your cardiovascular fitness level, making it more accurate than simply taking percentages of max heart rate alone.
Zone 2 (60-70% of HRR) is particularly valued in modern endurance training because it builds mitochondrial density and fat-burning efficiency without accumulating excess fatigue. Zone 4 and 5 training improves lactate threshold and VO2 max but requires significant recovery time. Most training plans recommend spending 75-80% of weekly volume in Zone 1-2 and 20-25% in Zone 3-5.
Frequently Asked Questions
What is Zone 2 training and why is it important?
Zone 2 is a moderate, aerobic intensity where you can hold a conversation but feel a noticeable effort. Training in Zone 2 builds mitochondrial density (the energy-producing organelles in muscle cells), improves fat oxidation efficiency, and builds your aerobic base without causing significant fatigue. It is the foundation of endurance fitness. Most research on elite endurance athletes shows they spend 70-80% of their training volume in Zone 2 or lower, despite their high-intensity race performances.
How do I find my actual maximum heart rate?
The 220 minus age formula has a standard deviation of about 10-12 bpm, meaning it can be significantly off for many individuals. To test your actual max HR, you need a hard effort: a ramp test on a stationary bike (increasing power every minute until failure), a 400m run at maximum effort, or a hard hill run. Your max HR during the test is your actual max. Always warm up thoroughly before a max HR test, and avoid it if you have any cardiovascular conditions without medical clearance.
Should I use heart rate or perceived exertion to guide training?
Both have value and they work best together. Heart rate is objective and measurable, but it is affected by heat, hydration, caffeine, illness, and stress, which can make it unreliable on some days. Rate of Perceived Exertion (RPE) on a 1-10 scale is subjective but captures your overall feel in real time. Using heart rate as a primary guide with RPE as a sanity check gives you the best of both tools. On days when heart rate runs abnormally high for your usual pace, trust your RPE and back off the effort.
What heart rate zone burns the most fat?
The highest proportion of fat is burned at lower intensities, around Zone 2. At very low intensities, almost all energy comes from fat. At higher intensities (Zone 4-5), carbohydrates become the dominant fuel source. However, total fat burned per hour is often higher at moderate intensities (Zone 3) than at very low intensities simply because more total calories are burned. For overall fat loss, total calorie deficit matters more than the fat-burning zone percentage.