How it works
Heart rate is the simplest honest measure of how hard you are working: easy walk, fat-burning endurance, threshold effort or all-out sprint. The calculator first estimates your maximum heart rate from your age, then divides it into five training zones. Add your resting heart rate and it switches to the Karvonen (heart-rate reserve) method, which accounts for your fitness and gives more personal targets.
max HR (Tanaka) = 208 − 0.7 × age · classic = 220 − age Karvonen target = resting HR + (max HR − resting HR) × intensityWorked example. Age 40: max HR = 208 − 28 = 180 bpm (the classic formula also gives 180 at this age). Zone 2, the “fat-burning” zone at 60–70%, is 108–126 bpm. With a resting pulse of 60, heart-rate reserve is 120, and the Karvonen zone 2 becomes 60 + 120 × 0.6 = 132 to 60 + 120 × 0.7 = 144 bpm.
The five zones
| Zone | Intensity | Talk test | Benefit |
|---|---|---|---|
| 1 — Very light | 50–60% | Easy conversation | Warm-up, recovery |
| 2 — Light (fat burn) | 60–70% | Full sentences | Aerobic base; fat is the main fuel |
| 3 — Moderate | 70–80% | Short sentences | Cardiovascular fitness |
| 4 — Hard | 80–90% | A few words | Lactate threshold, speed |
| 5 — Maximum | 90–100% | Can’t talk | Short intervals for trained athletes |
Is the fat-burning zone best for weight loss?
In zone 2 a larger share of energy comes from fat, but harder work burns more total calories per minute. Weight loss depends on total energy balance across the week, so most people do best mixing longer zone-2 sessions with shorter, harder ones.
Activity guidelines
The WHO and American Heart Association recommend 150–300 minutes a week of moderate activity (about 50–70% of max HR) or 75–150 minutes of vigorous activity (70–85%). The moderate and vigorous lines in the results show those ranges for your age.
How to measure resting heart rate
In the morning, before getting out of bed, find your pulse at the wrist or neck, count for 30 seconds and double it. Average three mornings. A normal adult resting rate is 60–100 bpm; endurance athletes are often 40–60.
Caution: formulas are estimates and your true maximum can differ by 10–12 bpm. Beta-blockers and some other medications change heart rate; if you have a heart condition, ask your doctor before vigorous exercise.
Track running speed with the pace calculator, daily calories with the TDEE calculator, and body composition with the body fat calculator.