Find your optimal fat-burning heart rate zone using simple and Karvonen methods
This calculator provides estimates only. Consult your GP or a healthcare professional for personalised advice.
This fat burning heart rate calculator helps you find the optimal heart rate zone for burning fat during exercise. It uses both the simple percentage method and the more accurate Karvonen method to give you personalised training zones based on your age and resting heart rate. Understanding your fat burning zone is essential for structuring effective workouts. The fat burning zone sits at 60-70% of your maximum heart rate, where your body relies more heavily on fat stores for energy. While higher-intensity exercise burns more total calories, working in the fat burning zone can be particularly effective for longer, sustained sessions. The British Heart Foundation recommends that adults aim for at least 150 minutes of moderate-intensity activity per week, which corresponds roughly to the fat burning zone. The NHS physical activity guidelines support this, encouraging a mix of moderate and vigorous exercise for overall health benefits. Maximum heart rate is estimated using the widely accepted formula of 220 minus your age. While individual variation exists, this provides a reliable starting point for most people. For a more personalised estimate, the Karvonen method factors in your resting heart rate, which reflects your current fitness level. Fitter individuals typically have lower resting heart rates and therefore a different heart rate reserve.
To calculate your fat burning heart rate zone: 1. Enter your age in years. The calculator uses this to estimate your maximum heart rate (220 minus age). 2. Optionally enter your resting heart rate in beats per minute. Measure this first thing in the morning before getting out of bed: place two fingers on your wrist or neck, count the beats for 30 seconds, and multiply by 2. If you leave this at 0, only the simple method will be used. 3. View your results. The simple method shows your fat burning zone (60-70% of max HR) and cardio zone (70-85% of max HR). If you entered a resting heart rate, you will also see Karvonen method zones, which are considered more accurate. 4. Use these zones during exercise. Wear a heart rate monitor or use a fitness watch to stay within your target zone. For fat burning sessions, aim for the 60-70% range. For cardiovascular fitness, work in the 70-85% range. 5. Compare the two methods. If the Karvonen values differ significantly from the simple method, the Karvonen zones are likely more reflective of your actual training intensity.
The calculator uses two methods to determine your fat burning heart rate zone: Simple percentage method: Maximum heart rate (maxHR) = 220 - age Fat burn zone = 60-70% of maxHR Cardio zone = 70-85% of maxHR Karvonen method (when resting heart rate is provided): Heart rate reserve (HRR) = maxHR - resting heart rate Fat burn zone = (HRR x 0.60 + resting HR) to (HRR x 0.70 + resting HR) Cardio zone = (HRR x 0.70 + resting HR) to (HRR x 0.85 + resting HR) The Karvonen method is more accurate because it accounts for individual fitness levels. A person with a resting heart rate of 50 bpm has a larger heart rate reserve than someone with a resting rate of 80 bpm, so their training zones are adjusted accordingly. For example, a 30-year-old with a resting heart rate of 60 bpm: maxHR = 190, HRR = 130. Karvonen fat burn zone = (130 x 0.60 + 60) to (130 x 0.70 + 60) = 138 to 151 bpm. This is higher than the simple method (114 to 133 bpm) because the resting heart rate shifts the zone upward.
Inputs: Age: 30. Resting heart rate: not provided.
Inputs: Age: 30. Resting heart rate: 60 bpm.
Inputs: Age: 50. Resting heart rate: not provided.
The 220-minus-age formula provides an estimate of maximum heart rate. For some individuals, actual max HR may be 10-20 bpm higher or lower. If you have had a supervised max HR test (e.g. during a VO2 max assessment), that measured value will be more accurate. Heart rate monitors and fitness watches (such as Apple Watch, Garmin, or Fitbit) can help you train within your target zone. Chest strap monitors tend to be more accurate than wrist-based optical sensors, particularly during high-intensity exercise. The fat burning zone does not mean you cannot burn fat at higher intensities. Higher-intensity exercise burns more total calories and can lead to greater overall fat loss, especially through excess post-exercise oxygen consumption (EPOC). However, the fat burning zone is ideal for longer sessions, recovery days, and people new to exercise. The British Heart Foundation recommends checking with your GP before starting a new exercise programme if you have a heart condition, high blood pressure, or any concerns about exercising safely. The NHS physical activity guidelines suggest 150 minutes of moderate activity or 75 minutes of vigorous activity per week for adults aged 19-64.