About the Target Heart Rate Calculator
A target heart rate calculator gives the beats-per-minute ranges corresponding to different training intensities. Training by heart rate zones keeps easy sessions genuinely easy and hard sessions genuinely hard, which is what drives adaptation rather than accumulating moderate fatigue.
The formula
Karvonen: THR = ((HRmax − HRrest) · intensity) + HRrestHRmax is estimated as 220 minus age, or more accurately 208 − 0.7 × age. The Karvonen method uses heart rate reserve — the gap between resting and maximum — which accounts for fitness better than a plain percentage of maximum.
How to use this calculator
- 1Enter your Age (years). The field starts at
35, which you can overwrite. - 2Enter your Resting Heart Rate (bpm). The field starts at
65, which you can overwrite. - 3Read the result straight away — it recalculates as you type, so there is no button to press. Use Share to copy a link that reopens the page with your exact numbers filled in.
Worked example
| Input | Value |
|---|---|
| Age (years) | 35 |
| Resting Heart Rate (bpm) | 65 |
Result
Max Heart Rate: 185 bpm
Heart Rate Reserve: 120 bpm
Zone 1 (Warm-up): 125–137 bpm
Zone 2 (Fat Burn): 137–149 bpm
Zone 3 (Aerobic): 149–161 bpm
Zone 4 (Anaerobic): 161–173 bpm
Zone 5 (Max): 173+ bpm
Those are the values the page loads with, so you can reproduce this result yourself and then change one field at a time to see what drives the outcome.
Understanding your result
Zones correspond to different physiological adaptations. Below 60 percent builds aerobic base and aids recovery. Sixty to 70 percent improves fat oxidation and endurance. Seventy to 80 percent develops aerobic capacity. Above 80 percent works on lactate threshold and VO₂ max, and cannot be sustained for long.
The 220-minus-age formula has a standard deviation of about 10 to 12 beats per minute, meaning your actual maximum could easily be 20 beats either side of the estimate. Zones built on it are therefore approximate. A field test or lab assessment gives far better numbers, and rate of perceived exertion is a useful cross-check.
Things worth knowing
- Resting heart rate is best measured immediately on waking, before getting up. A falling resting rate over months indicates improving fitness.
- The Karvonen method using heart rate reserve is more accurate than a plain percentage of maximum heart rate.
- Heart rate drifts upward during long efforts at constant pace — cardiac drift — from heat and dehydration.
- Caffeine, illness, heat, altitude, and poor sleep all shift heart rate at a given effort.
- Chest strap monitors are considerably more accurate than wrist optical sensors during high-intensity work.
Frequently asked questions
What is my maximum heart rate?+
The common estimate is 220 minus your age, though 208 − 0.7 × age is more accurate. Individual variation is around 10 to 12 beats either side, so a field test gives a much better figure.
What heart rate should I train at?+
60 to 70 percent of maximum for easy aerobic work, which should be most of your training, and 80 percent or above for interval sessions. The middle range is useful for tempo work but easy to overuse.
What is the fat burning zone?+
Around 60 to 70 percent of maximum, where fat provides the largest proportion of fuel. Higher intensities burn more total calories and more total fat, so the zone matters less for weight loss than its name suggests.
Why is my heart rate higher than usual today?+
Heat, dehydration, poor sleep, caffeine, stress, illness, or accumulated training fatigue all raise heart rate at a given effort. A resting rate several beats above normal is a reasonable signal to train easier.