Heart Rate Zone Calculator
Find your 5 training zones and your Zone 2 fat-burning range in seconds. Free, private, and running entirely in your browser — nothing is uploaded. Your Apple Watch already uses zones like these in the Workout app; here is how to personalize them.
Required
Optional — enables Karvonen
Optional — overrides formula
Enter your age above and your zones appear instantly — no submit button, no upload.
How to use it
- 1Enter your age. That is all you need for a solid estimate of your maximum heart rate and all five zones.
- 2Add your resting heart rate (optional) to unlock the Karvonen method for more personalized zones. Check it first thing in the morning, or read it from the Apple Health app.
- 3Know your true max? If you have measured it in a lab or a hard field test, type it into "Known max HR" to override the formula.
- 4Read your Zone 2 range and the full table, which update live as you type.
- 5Copy the numbers to your Apple Watch: iPhone → Settings → Workout → Heart Rate Zones → Manual, then enter these bpm boundaries.
Understanding your heart rate zones
Heart rate zones are simply bands of exercise intensity, measured as a share of how hard your heart can possibly work. Train in the right zone and every workout has a clear purpose: easy days stay easy, hard days deliver, and you stop grinding through the "gray zone" that leaves you tired without getting fitter. Your Apple Watch already colors your effort into zones during a workout — this calculator just lets you set those boundaries from numbers that actually fit you instead of generic defaults.
Why we use the Tanaka formula, not 220 − age
Almost every gym poster still shows "220 minus your age" for maximum heart rate. The problem is that this rule was never based on solid research — it came from a rough eyeballing of old data and can be off by 10–20 beats per minute. A 2001 meta-analysis by Tanaka and colleagues, pooling data from thousands of people, produced a far more reliable estimate: Max HR = 208 − (0.7 × age). It tends to give younger adults a slightly lower max and older adults a higher one than the 220 rule, which matches what labs actually measure. That is why this tool defaults to Tanaka — but if you have a genuine measured maximum from a stress test or an all-out effort, always prefer that and enter it as your override.
Percentage of max vs. the Karvonen method
There are two common ways to turn a maximum heart rate into zones. The percentage-of-max method takes flat slices of your max: Zone 1 is 50–60%, Zone 2 is 60–70%, Zone 3 is 70–80%, Zone 4 is 80–90%, and Zone 5 is 90–100%. It is simple and it is what most watches use out of the box.
The Karvonen method is more personal because it works from your heart rate reserve — the gap between your maximum and your resting heart rate. The formula is target = ((Max HR − Resting HR) × intensity%) + Resting HR. Because a fitter person with a lower resting heart rate has a wider reserve, Karvonen shifts their zones to reflect that, usually landing a few beats higher than the plain percentage method. If you entered your resting heart rate above, this calculator shows both tables side by side so you can compare.
What each zone is for
Zone 1 (50–60%) is recovery — warm-ups, cool-downs, and easy walks. Zone 2 (60–70%) is the aerobic base and fat-burning zone where endurance is built; most of your training time belongs here. Zone 3 (70–80%) is a moderate "tempo" effort that improves aerobic efficiency. Zone 4 (80–90%) is threshold work that raises the pace you can hold before lactate piles up. Zone 5 (90–100%) is all-out interval territory for peak speed and power, used sparingly. A common, well-supported approach is to spend roughly 80% of your training easy (Zones 1–2) and 20% hard (Zones 4–5).
Setting these zones on your Apple Watch
watchOS can show heart rate zones live during any workout, and it lets you set them manually instead of relying on Apple's automatic calculation. On your iPhone, open Settings → Workout → Heart Rate Zones (you can also reach zone settings from the Fitness app), switch to Manual, and enter the bpm boundaries from the table above. Now, when you glance at your wrist mid-run, the zone your watch reports is measured against numbers that actually match your body — so your Zone 2 easy days stay genuinely easy.
Frequently asked questions
How do I calculate my heart rate zones?
First estimate your maximum heart rate. This calculator uses the Tanaka formula (208 − 0.7 × age), which is more accurate than the old 220 − age rule. Your five zones are then set as percentage bands of that maximum (Zone 1 = 50–60% up to Zone 5 = 90–100%). Enter your resting heart rate too and it also shows the more personalized Karvonen (heart-rate-reserve) zones.
What is Zone 2 heart rate and why does everyone talk about it?
Zone 2 is a comfortable, conversational effort at roughly 60–70% of your maximum heart rate. It is the intensity where your body relies most on fat for fuel and builds aerobic (mitochondrial) capacity, which is why coaches recommend spending most easy training time there. It should feel almost too easy — that is the point.
Percentage method vs. Karvonen method — what's the difference?
The percentage-of-max method takes a flat percentage of your maximum heart rate. Karvonen works from your heart rate reserve (max HR minus resting HR) and then adds your resting HR back in. Because it accounts for how fit your resting heart rate says you are, Karvonen gives more personalized boundaries — usually a little higher than the plain percentage method.
Can I set these heart rate zones on my Apple Watch?
Yes. watchOS supports manual heart rate zones in the Workout app. On your iPhone go to Settings → Workout → Heart Rate Zones (or set them in the Fitness app), choose Manual, and type in the bpm boundaries this calculator gives you. Your watch will then show and buzz the correct zones during workouts.
Is the Tanaka formula better than 220 − age?
For most people, yes. The 220 − age rule was never derived from careful research and tends to overestimate max heart rate for younger adults and underestimate it for older adults. The Tanaka formula (208 − 0.7 × age) came from a large meta-analysis and tracks measured maximums much more closely across ages.
Is this calculator private?
Completely. Every calculation runs in your browser using JavaScript. Your age, resting heart rate, and results are never sent to any server — nothing is uploaded.
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Want deeper analysis?
See how much time your Apple Watch actually logs in each zone, track your resting heart rate trend, and let AI surface patterns across all your health data.
This tool is for general fitness information and is not medical advice. Talk to a doctor before starting a new exercise program.