Your target heart rate is the beats-per-minute range you aim for during exercise to train at the right intensity for your goal. Going too easy limits results; going too hard too often risks burnout. Heart-rate zones give you an objective gauge that works whether you are walking, cycling, or doing intervals.
This target heart rate calculator estimates your maximum heart rate from your age, then maps out your fat-burn, cardio, and peak zones in seconds. Enter an optional resting heart rate to use the more personalized Karvonen method.
How the heart rate zones calculator works
The calculator first estimates your maximum heart rate using the classic formula Max HR = 220 - age. It then applies intensity percentages to that maximum to define three training zones: fat-burn (50-70%), cardio (70-85%), and peak (85-95%).
If you also enter your resting heart rate, the tool switches to the more individualized Karvonen method, which factors in your fitness baseline. The Karvonen formula is:
Target HR = (Max HR - Resting HR) x Intensity + Resting HR
Here, "Max HR - Resting HR" is your heart rate reserve. Each zone boundary uses its intensity percentage (for example 0.70 and 0.85 for the cardio zone). The only inputs needed are your age and, optionally, your resting heart rate in beats per minute. Results update live as you type, in both metric and US contexts, since heart rate uses the same beats-per-minute unit everywhere.
Worked example
Take a 40-year-old with a resting heart rate of 60 bpm. Max HR = 220 - 40 = 180 bpm. Heart rate reserve = 180 - 60 = 120 bpm.
Using the Karvonen method for the cardio zone (70-85%): - Lower: 120 x 0.70 + 60 = 84 + 60 = 144 bpm - Upper: 120 x 0.85 + 60 = 102 + 60 = 153 bpm
So this person's cardio zone is roughly 144 to 153 bpm. Without a resting HR, the simple method gives 180 x 0.70 = 126 to 180 x 0.85 = 153 bpm.
Things to keep in mind
- The 220 - age formula is a population estimate and can be off by 10-12 bpm for any individual, so use the zones as guides rather than exact limits.
- Medications such as beta-blockers, plus caffeine, stress, heat, and dehydration, can all shift your actual heart rate at a given effort.
- Karvonen results are only as accurate as your resting heart rate measurement; take it first thing in the morning before getting up for the best reading.
- Heart-rate training is general fitness guidance, not medical advice. If you have a heart condition or are new to exercise, check with a doctor before targeting high-intensity zones.
Frequently asked questions
What is a good target heart rate for fat burning?
The fat-burn zone is 50-70% of your maximum heart rate (220 minus your age). For a 35-year-old, max HR is 185 bpm, so the fat-burn zone is about 93 to 130 bpm. This lower-intensity range lets you sustain effort longer.
What is the difference between the simple and Karvonen methods?
The simple method applies an intensity percentage directly to your max heart rate. The Karvonen method uses your heart rate reserve (max minus resting HR), giving a more personalized target. Enter a resting heart rate in the calculator to switch to Karvonen automatically.
How do I measure my resting heart rate?
Measure it first thing in the morning while still lying down, before any caffeine or activity. Count your pulse for 60 seconds, or use a fitness tracker. A typical resting heart rate for adults is 60-100 bpm; fitter people often sit lower.
Is 220 minus age accurate for max heart rate?
It is a widely used estimate, but it can vary by about 10-12 bpm from your true maximum. It works well as a starting point for setting training zones. For precision, a supervised exercise test measures your actual maximum heart rate.
Which heart-rate zone should I train in?
It depends on your goal. The fat-burn zone (50-70%) suits longer steady sessions and beginners. The cardio zone (70-85%) builds aerobic fitness. The peak zone (85-95%) is for short, intense intervals and should be used sparingly with adequate recovery.
Why does my heart rate not match the calculator?
Real-time heart rate is affected by caffeine, stress, heat, sleep, hydration, and medications like beta-blockers. The calculator gives estimated target ranges, not exact readings. Use it to guide effort, and adjust to how you feel during exercise.