Zone 2 is the heart rate range where your body burns fat and builds aerobic fitness
Zone 2 is the second of five heart rate zones used in fitness training. It sits between your resting heart rate and the point where your body starts to rely more on carbohydrates than fat for fuel. Most people find Zone 2 somewhere between 50 and 70 percent of their maximum heart rate, though the exact number depends on your age, fitness level, and how you measure it.
The reason Zone 2 matters is practical: it is the zone where you can sustain effort for a long time while still improving your aerobic system. You can hold a conversation but not sing. Many runners, cyclists, and endurance athletes spend a large portion of their training time here because the work is hard enough to build fitness but not so hard that you need days to recover.
To calculate your Zone 2 range, you need two numbers: your maximum heart rate and your resting heart rate. Once you have those, a simple formula gives you the upper and lower bounds of the zone. Most fitness apps and smartwatches can do this math for you, but understanding the calculation yourself means you can check their work and adjust if the numbers do not feel right during a workout.
Key Takeaways
- Zone 2 is roughly 50 to 70 percent of your maximum heart rate, but the exact range depends on whether you use the simple percentage method or the Karvonen formula, which accounts for resting heart rate.
- To calculate it yourself, you need your maximum heart rate (usually estimated as 220 minus your age) and your resting heart rate (measured first thing in the morning before getting out of bed).
- The Karvonen formula is more accurate for most people because it factors in your current fitness level, while the simple percentage method is faster but less precise.
- Your Zone 2 range will shift as your fitness improves and your resting heart rate drops, so recalculate every few months if you are training regularly.
- A chest strap monitor or smartwatch gives you real-time feedback during workouts, but you can also count your pulse manually for a quick check.
Find your maximum heart rate
Your maximum heart rate is the highest number of beats per minute your heart can reach. The quickest way to estimate it is to subtract your age from 220. A 40-year-old would have an estimated maximum of 180 beats per minute (220 − 40 = 180). This formula works reasonably well for most people, though it is less accurate the older you are.
If you want a more accurate number, you can measure your actual maximum heart rate during a hard workout. Run, cycle, or row at high intensity for a few minutes until you cannot push any harder, then note the highest heart rate your monitor records. This is genuinely your maximum, not an estimate. However, this method is physically demanding and carries some risk, so most people stick with the age-based estimate unless they are training seriously.
Write down your maximum heart rate — you will need it for the next step. If you are using a fitness app or smartwatch, enter your age and let the app calculate it for you.
Measure your resting heart rate
Your resting heart rate is how many times your heart beats per minute when you are completely at rest. Measure it first thing in the morning, before you get out of bed, drink coffee, or check your phone. Sit or lie still for at least five minutes, then count the beats in your wrist or neck for 60 seconds, or count for 15 seconds and multiply by four.
If you have a smartwatch or fitness tracker, it likely measures resting heart rate automatically overnight. Check the app in the morning to see the number. Most devices average your resting heart rate over several nights, which gives a more reliable picture than a single measurement.
Resting heart rate varies by fitness level. An untrained person might have a resting rate of 70 to 80 beats per minute. Someone who trains regularly might be at 50 to 60. The fitter you become, the lower your resting heart rate typically drops, which is why you should remeasure it every few months if you are training consistently.
Calculate Zone 2 using the Karvonen formula
The Karvonen formula is the most accurate method for most people because it accounts for your resting heart rate, which reflects your current fitness level. Here is the step-by-step calculation:
- Subtract your resting heart rate from your maximum heart rate. This gives you your heart rate reserve. Example: 180 − 60 = 120.
- Multiply your heart rate reserve by 0.50 (the lower boundary of Zone 2). Example: 120 × 0.50 = 60.
- Add your resting heart rate back in. Example: 60 + 60 = 120 beats per minute. This is your Zone 2 lower bound.
- Multiply your heart rate reserve by 0.70 (the upper boundary of Zone 2). Example: 120 × 0.70 = 84.
- Add your resting heart rate back in. Example: 84 + 60 = 144 beats per minute. This is your Zone 2 upper bound.
In this example, Zone 2 is 120 to 144 beats per minute. During a Zone 2 workout, you would aim to keep your heart rate in that range. The Karvonen method shifts your zones as your fitness improves because your resting heart rate drops, which automatically lowers all your zones.
Calculate Zone 2 using the percentage method
The percentage method is simpler but less precise. It skips the resting heart rate and calculates zones as a straight percentage of your maximum heart rate. Zone 2 falls between 50 and 70 percent of your maximum.
Using the same example (maximum heart rate of 180): multiply 180 by 0.50 to get the lower bound (90 beats per minute) and multiply 180 by 0.70 to get the upper bound (126 beats per minute). Your Zone 2 would be 90 to 126 beats per minute.
Notice that this range is lower than the Karvonen result. The percentage method tends to underestimate zones for fit people and overestimate them for unfit people. It works well enough for casual training, but if you are following a structured training plan, the Karvonen formula will be more accurate.
Use your fitness app or smartwatch to track Zone 2
Most fitness apps and smartwatches calculate your zones automatically once you enter your age and, ideally, your resting heart rate. Open the settings in your app — usually under "Profile" or "Heart Rate Zones" — and check what method it is using and what numbers it calculated. Some apps let you override the automatic calculation and enter your own zones if you have measured them yourself.
During a workout, your device will display your current heart rate and show which zone you are in, usually with a color code (Zone 2 is often green or blue). Some apps will vibrate or alert you if you drift above or below your target zone, which helps you stay consistent without constantly checking the screen.
If your app's zones do not feel right during a workout — if you are breathing hard but the app says you are in Zone 2, or if you are barely working but it says you are in Zone 3 — recalculate your maximum and resting heart rates. Your fitness level may have changed, or your initial estimates may have been off.
Check your Zone 2 with a manual pulse count
You do not need a device to verify your heart rate. During a workout, stop for a moment and find your pulse on your wrist or neck. Place two fingers (index and middle) lightly on the inside of your wrist, below the thumb, or on the side of your neck below your jaw. Count the beats for 15 seconds, then multiply by four to get beats per minute.
A manual count is useful as a sanity check if your device seems wrong, or if you want to confirm your zones without buying a monitor. The downside is that your heart rate starts to drop the moment you stop moving, so you need to count quickly. For a more accurate manual measurement, count for a full 60 seconds while still moving or immediately after stopping.
If your manual count is consistently higher or lower than what your device shows, your device may need recalibration. Most smartwatches and chest straps can be recalibrated in their settings, or you may need to re-enter your personal data.
Recalculate your zones as your fitness improves
As you train regularly, your resting heart rate will drop and your fitness level will improve. This means your heart rate zones shift downward — the same effort that used to put you in Zone 3 might now keep you in Zone 2. Recalculate your zones every two to three months if you are training consistently, or whenever you notice that your workouts feel easier than the zones suggest.
To recalculate, measure your resting heart rate again (take the average over three mornings for accuracy), then run the Karvonen formula again with the new number. You may also want to test your maximum heart rate again if it has been more than a year since your last estimate, though the age-based formula usually stays accurate enough for most people.
Some fitness apps update your zones automatically based on data they collect during your workouts, so check your app settings to see if this feature is turned on. If it is, you do not need to manually recalculate — the app will do it for you.
Frequently Asked Questions
What is the difference between Zone 2 and Zone 3?
Zone 3 is harder than Zone 2 — your heart rate is higher and you are breathing harder. Zone 2 is where you can sustain effort for hours. Zone 3 is where you build speed and power but cannot maintain it as long. Most training plans use Zone 2 for base building and Zone 3 for tempo or threshold work.
Should I use the Karvonen formula or the percentage method?
Use Karvonen if you have measured your resting heart rate and want the most accurate zones. Use the percentage method if you want a quick estimate or do not have a resting heart rate measurement. Karvonen is more precise, especially if you are fit or unfit compared to average.
Why does my smartwatch show a different Zone 2 than my calculation?
Your watch may be using a different formula, or it may have estimated your maximum heart rate differently than you did. Check your watch settings to see what age and resting heart rate it is using. If those numbers are wrong, update them and recalculate. You can also manually enter your zones in most apps if you want to override the automatic calculation.
Can I train in Zone 2 every day?
Yes, Zone 2 is low enough intensity that most people can do it daily without overtraining. Many endurance athletes spend 80 percent of their training time in Zone 2. The key is that it should feel sustainable — you should be able to hold a conversation and recover fully within a day or two.
What if my resting heart rate is very high?
A high resting heart rate can mean you are not fully recovered from recent training, you are stressed, or you are less fit than you think. Measure it over several mornings to get an average, and measure it under the same conditions each time (same time of day, same amount of sleep). If it stays high, focus on easier training and more recovery before pushing hard.