Two people can run side by side at the same pace and be doing completely different workouts. One is cruising in an easy aerobic effort while the other is gasping near their limit. Heart rate training zones turn that invisible difference into a number you can actually steer by.
This guide explains what the five zones are, how to find yours using the simple max-heart-rate method and the more personal Karvonen method, and how to mix the zones across a training week.
What are heart rate training zones?
A heart rate training zone is a range of beats per minute that corresponds to a particular level of effort. Instead of guessing whether you are working "moderately" or "hard," you watch your heart rate and let it tell you which physiological system you are training.
Most coaches use a five-zone model. Each zone trains something slightly different, from easy fat-burning aerobic work at the bottom to all-out anaerobic effort at the top. The zones are defined as percentages of either your maximum heart rate or your heart rate reserve.
Estimating your maximum heart rate
Your maximum heart rate (max HR) is the fastest your heart can beat during all-out effort. The classic estimate is simple:
- Max HR = 220 minus your age
So a 40-year-old gets an estimated max of 180 beats per minute.
It is quick and good enough to get started, but it has real limits. The 220-minus-age formula is a population average, and your true maximum can sit well above or below it. Two people the same age can differ by 20 beats per minute or more. It also says nothing about your fitness level. The only truly accurate way to find your max is a supervised maximal exercise (stress) test.
Why resting heart rate matters
Your resting heart rate (RHR) is your pulse when you are calm and still, ideally measured first thing in the morning. It is a useful fitness marker on its own: as your aerobic conditioning improves, your resting heart rate tends to drop because your heart pumps more blood per beat.
RHR also unlocks a more personal way to set zones. The gap between your maximum and resting heart rate is called your heart rate reserve (HRR), and it reflects how much "room" your heart has to work with. Using it produces zones tailored to you rather than to the average person your age.
The Karvonen (heart rate reserve) method
The Karvonen method, named after Finnish physiologist Martti Karvonen, builds your target heart rate from your heart rate reserve instead of from max HR alone. In words, it works like this:
- Subtract your resting heart rate from your maximum heart rate to get your heart rate reserve.
- Multiply that reserve by the intensity percentage you are aiming for.
- Add your resting heart rate back on.
The result is the target heart rate for that intensity. Because the calculation folds in your resting heart rate, the zones shift to match your conditioning. The American College of Sports Medicine (ACSM) recommends the heart rate reserve approach for exercise prescription precisely because it is more accurate than a plain percentage of max, especially for very fit or very unfit people.
You do not have to run the arithmetic by hand. The heart rate zone calculator applies the Karvonen method and gives you all five ranges from your age and resting pulse.
The five training zones
Here is what each zone targets. The percentages below are of maximum heart rate; the Karvonen method shifts the exact beat numbers but the structure is the same.
- Zone 1 - warm-up (50 to 60 percent). Very light effort. Used for warming up, cooling down, and active recovery. Builds a base and improves circulation with minimal stress.
- Zone 2 - fat burn (60 to 70 percent). Comfortable, conversational pace. Develops aerobic endurance and trains your body to use fat efficiently as fuel. This is where most easy mileage should sit.
- Zone 3 - cardio (70 to 80 percent). Moderate to hard. Improves aerobic capacity and cardiovascular efficiency. You can still talk, but only in short sentences.
- Zone 4 - anaerobic (80 to 90 percent). Hard effort that pushes toward your lactate threshold. Raises your ability to sustain fast paces and boosts speed and power.
- Zone 5 - maximum (90 to 100 percent). All-out effort you can only hold for short bursts. Reserved for intervals and sprints; develops peak performance and is demanding to recover from.
The "fat burn zone" myth
Gym equipment loves to label Zone 2 the "fat burning zone," and it is true that a larger share of the calories you burn there comes from fat. But share is not the same as total.
Higher-intensity zones burn far more total calories per minute, and a meaningful chunk of those still come from fat. They also keep burning energy after you stop. So if fat loss is the goal, what matters most is your overall calorie balance, not which zone the percentages say is "fat burning." To see where your daily calorie budget sits, start with the TDEE calculator.
In short: train in lower zones to build an aerobic base and protect recovery, and use higher zones when you want to maximize calorie burn or improve speed.
Putting zones into a weekly plan
A common and well-supported structure is the 80/20 rule: roughly 80 percent of your weekly training time in the easy zones (1 and 2) and about 20 percent in the hard zones (4 and 5), with Zone 3 used sparingly.
A simple week might look like this:
- Two to three easy Zone 2 sessions for aerobic base and fat metabolism.
- One harder session with intervals reaching Zone 4 or Zone 5.
- One Zone 1 recovery session, plus a longer easy effort.
Keeping most of your volume genuinely easy is what lets your hard days be hard. If you also lift weights, your strength sessions live on a different scale of intensity. You can track and progress those with the one-rep max calculator so your conditioning and strength work complement rather than fight each other.
Frequently asked questions
Is the Karvonen method better than 220 minus age?
For most people, yes. Both rely on an estimated maximum heart rate, but Karvonen also factors in your resting heart rate, so the zones reflect your fitness rather than just your age. ACSM favors the heart rate reserve approach for this reason.
Do I need a chest strap or will a watch work?
A wrist-based optical sensor is fine for everyday zone training and trend tracking. Chest straps are more accurate during fast changes in intensity and high-effort intervals, so serious interval work benefits from one.
Which zone should I train in to lose weight?
There is no single magic zone. Easy Zone 2 work is sustainable and builds your aerobic engine, while higher zones burn more total calories in less time. Weight loss ultimately depends on your overall energy balance, so a mix works best.
How do I find my resting heart rate?
Measure your pulse for a full minute right after you wake up, before getting out of bed, on several mornings, and take the average. A fitness tracker worn overnight will estimate it for you.
This article is for general education and is not medical advice. Check with a healthcare provider before starting a new exercise program, especially if you have a heart condition or other health concerns.