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❤️ Heart Rate Zones
Compute the 5 standard training heart rate zones using the Karvonen formula. Inputs: age and optional resting heart rate. Output: max HR estimate (220 − age) and 5 zones from 50% to 100% intensity.
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Examples
30yo, resting 60bpm
Output
Max ~190 · Zone 1 95-114 (warm-up) · Zone 2 114-133 (fat burn) · Zone 3 133-152 (cardio) · Zone 4 152-171 (aerobic) · Zone 5 171-190 (peak)Frequently asked questions
How accurate is 220-age for max HR?
Roughly ±10 bpm. Individual variation is large. For precision, do a max-effort test or use a more advanced formula like Tanaka (208 − 0.7×age).
Which zone for fat burning?
Zone 2 (60-70% max HR) burns the highest *percentage* of calories from fat. Zone 4-5 burns more total calories. For weight loss, both work — pick what you'll sustain.
About this tool
Heart Rate Zones runs entirely in your browser using standard Web APIs. No data is sent to any server. The source for this tool is in our public GitHub repository.
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Why this tool
vs typical free web-tool sites
| 1vw | Typical free site | |
|---|---|---|
| Price | Free | Free |
| Signup required | No | Often (for premium features) |
| Ads inside the tool | No | Yes (banner + video) |
| Data sent to server | No (browser-only) | Yes (inputs analyzed for ads) |
| Total tools | 96 | Often <20 or scattered across sites |
| Bookmarkable URL per tool | Yes | Mixed |
| Loads in under 1s | Yes (static) | Often slow (ad tracking) |
| Multilingual | EN / ES / PT / FR / DE | Usually EN only |
| Open source | Yes | No |