What is Fat Burning Zone & How to Calculate Your Rate

Written by
Emily @ 8fit
Written by
Emily @ 8fit
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If you’ve ever hopped on a treadmill, elliptical or stationary bike at the gym, you may have noticed an interesting heart rate range chart with ages on one axis and “zones” on another. If you use these machines often, it’s likely you even memorized the heart rate ranges for your age group too, because let’s be honest, there’s little else to look at while pedaling for 30 minutes on that stationary bike.

Before we talk specifically about the fat-burning zone and whether it’s even accurate or useful, let’s discuss how the different heart rate zones on the chart are calculated. First off you take the maximum heart rate for your age and multiply it by a certain percentage. So, yes, math is involved.

Your maximum heart rate is 220 minus your age. This is the maximum number of times your heart should beat per minute during exercise. Of course, this number could vary slightly based on the level of your athleticism, but in most cases, it’s pretty accurate. In the next part of the equation, you multiply your maximum heart rate by a percentage to find how quickly your heart should beat when exerting exercise effort. For example, if you’re participating in moderate or very light intensity exercise on recovery day, take your maximum heart rate and multiply it by 0.5 and 0.6 to find your heart rate range.

Let’s see what that looks like for a 35-year-old woman:

  • 220 – age 35 = 185

  • 185 * 0.5 = 92.5 (moderate intensity exercise)

  • 185 * 0.6 = 111 (light intensity exercise or recovery day)

The above illustrates that when exercising for recovery at a very light effort, this woman’s heart rate should be between 92.5 and 111 beats per minute.

Exercise heart rate zones

Of course, we aren’t always training at a very light effort. If you’re trying to increase your working on your endurance, odds are you’re exercising at a light effort. If you’re an athlete working on explosiveness, hard or maximum effort is where you focus.

Here are the different ranges:

  • Very light (50-60%) – Improves overall health and helps recovery; very easy on breathing and muscles

  • Light (60-70%) – Improves basic endurance and burns fat; characterized by comfortable, easy breathing and light sweating

  • Moderate (70-80%) – Improves aerobic (cardio) fitness; light muscle fatigue, easy breathing, and moderate sweating

  • Hard (80-90%) – Increases maximum performance capacity; muscle fatigue and heavy breathing

  • Maximum (90-100%) – Develops maximum performance and speed; should be very exhausting for both breathing and muscle fatigue alike

Like the chart above illustrates, exercising at 60-70% of your total effort is one of the most effective ways to burn fat. To reap the most physical benefits it’s best to exercise within this heart rate range for 40-80 minutes.

  • Here is a fat-burning zone calculator, or use the equation below: 220 – [your age] = [your maximum heart rate]

  • [your maximum heart rate] * 0.6 = [minimum fat-burning zone heart rate]

  • [your maximum heart rate] * 0.7 = [minimum fat-burning zone heart rate]

Let’s use the same example we used above. For someone who is 35, the fat-burning zone is…

  • 220 – age 35 = 185

  • 185 * 0.6 = 111

  • 185 * 0.7 = 129.5

This person should do light exercise for 40 or more minutes, keeping their heart rate between 111 and 129.5 beats per minute.

Fat-burning zone heart rate chart

Curious what your fat-burning zone is? Use the equation above to calculate the exact metric or use our handy guidelines below for a rough estimate. When entering fat-burning mode, your heart should be between 60 and 70 percent of your maximum heart rate. That means a 20-year old should have a heart rate between 120 and 140 beats per minute during light exercise. Someone older, for example, aged 60 should have a heart rate between 96 and 112 beats per

  • 20 years old: 120-140 BPM (beats per minute)

  • 30 years old: 114-133 BPM

  • 40 years old: 108-126 BPM

  • 50 years old: 102-119 BPM

  • 60 years old: 96-112 BPM

  • 70 years old: 90-105

Is fat-burning mode legit?

It’s true that the body burns a greater percentage of fat at lower than higher intensities, but that doesn’t mean that slow, steady-state workouts are the most effective way to lose weight and keep it off. Here’s why: The general recommendation is to exercise in your fat-burning heart rate zone for 40+ minutes — that’s a long time. Not everyone has the luxury of fitting in that long a workout.

So, yes. The fat-burning zone is legit. At 60 to 70 percent of your maximum heart rate, the calories that your body burns are mostly calories from fat. If you go on a brisk walk for one hour, you’ll likely burn between 225 and 300 calories depending on your biometrics and fitness level. That said, you could burn the same amount of calories in half, maybe a quarter, of the time by doing a HIIT workout.

Studies show that HIIT (high-intensity interval training) workouts burn more overall calories in a shorter amount of time. Here at 8fit, we recommend that you do HIIT workouts 3-5 times per week, mixing in other forms of exercise like that steady-state cardio (light jog, brisk walk, bike ride, or elliptical machine) two or more times per week.

How to measure your heart rate

If you want to put this into practice, there are a few different ways to measure your heart rate — some more accurate than others.

  • Check your radial pulse: Place two fingers on your wrist between the bone and the tendon over your radial artery closer to the thumb side of your wrist. Once you find your pulse, count the number of beats in 15 seconds. Multiply this number by four, and you have your heart rate.

  • Chest strap heart rate monitor: There are many chest straps on the market. Some are built into watches, apps or cardio machines. They measure your heart rate, then transmit that number to another device. It is one of the more accurate assistive heart rate devices because it closely mimics an EKG machine by measuring electrical pulses.

  • Wristwatch heart rate monitor: Brands like Apple, Garmin, Polar, and Fitbit measure your heart rate as you exercise using light. On the underside of the band, a light illuminates your capillaries and senses when blood pumps through, noticing the change in color.

  • Heart rate apps:You can also use an app on your smartphone to check your pulse. You do this by placing your finger over the camera while it detects changes in your skin color (blood pumping into your finger) — similar to how a heart rate monitor wristwatch works.

  • Exercise machines:You’ve probably noticed those metal hand grips on your favorite cardio machine. They check your heart rate during exercise but they aren’t always reliable.

Now that you know how to measure your heart rate put it into practice and find your fat-burning zone. It’s valuable to understand what exercising at this level feels like so you can be sure you’re exerting the right amount of effort to reach your unique goals.

Sign up for 8fit to log your fat-burning activities, HIIT workouts, yoga sessions, and more.

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