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Heart Rate Zones Calculator
x402
Heart Rate Zones Calculator is a paid API for AI agents from fitness-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).
Calculates estimated maximum heart rate (Tanaka and Fox formulas) and five training zones by percentage of max or heart-rate reserve (Karvonen method) from age and optional resting HR.
Price / call$0.02
Success—
StatusUnknown
How this service works
Estimated maximum heart rate (Tanaka, Fox) and five training zones as percent of max or by heart-rate reserve (Karvonen).
Output
Returns both Tanaka and Fox estimated maximum heart rates, the max HR actually used in calculations, resting HR and heart rate reserve (if provided), five labeled training zones each with a bpm min/max range and percent-of-reserve values, the calculation method name, a summary, verdict, disclaimer, and any degraded-mode flags or reasons.
Example use cases
Zone 2 cardio training plan
“I'm 45 years old and want to train in zone 2 for endurance — what heart rate range should I stay in?”
Athlete with measured max HR
“My measured max heart rate is 187 bpm and I'm 31 — can you calculate my five training zones using that actual number instead of an estimate?”
Beginner learning training zones
“I'm 55 years old with a resting heart rate of 65 bpm, just starting to exercise — can you show me all five heart rate zones using the Karvonen reserve method so I know what bpm to target?”
Technical details
Endpoint
GEThttps://fitness-calc.x402tookit.com/heart-rate-zones?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need structured, formula-attributed heart rate zone data (Tanaka, Fox, Karvonen) with per-zone bpm ranges rather than a generic static chart. Ideal when the user supplies their resting HR for the more precise Karvonen/reserve method, or when you need to compare estimated vs measured max HR in one call.
Side effects
- Age outside valid range (10–100) returns an error or degraded result
- Missing required 'age' parameter causes a 400-level error
- Providing a physiologically implausible measured max HR may trigger a warning or degraded flag
- Resting HR provided without age still requires age as the required field
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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