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Heart Rate Zone Calculator

Estimates maximum heart rate from age (Tanaka or Fox formula) and computes the five training zones, using the Karvonen heart-rate-reserve method when resting heart rate is supplied.

When to use

You need training heart-rate ranges (zones 1–5) for an adult from age, optionally refined by resting heart rate.

Do not use when: The person takes heart-rate-limiting medication (e.g. beta blockers) or has a measured maximum heart rate from a test (use that instead of an age formula).

Formula

max_hr = 208 − 0.7·age (Tanaka) or 220 − age (Fox). Percent-of-max: zone = max_hr × %. Karvonen: target = (max_hr − resting) × % + resting. Zones: 50–60, 60–70, 70–80, 80–90, 90–100%.

Inputs

Parameter	Type	Unit	Required	Description
`age_years`	number	years	yes	Age in years. Range: ≥ 5, ≤ 120
`resting_heart_rate`	number	bpm	no	Optional resting heart rate; when given, zones use the Karvonen (heart-rate reserve) method. Range: ≥ 25, ≤ 150
`max_hr_formula`	enum: tanaka \| fox		default tanaka	Formula for maximum heart rate. Tanaka (2001) is more accurate across ages than the classic 220 − age.

Outputs

Output	Type	Unit	Description
`max_heart_rate`	number	bpm	Estimated maximum heart rate.
`method`	string		'karvonen' when resting HR provided, otherwise 'percent_of_max'.
`zones`	list		Five zones with intensity range, lower and upper bpm and purpose.

Example

Age 30, Tanaka, no resting HR: {"age_years":30} → {"max_heart_rate":187,"method":"percent_of_max"}

Age 40, resting 60, Fox: {"age_years":40,"resting_heart_rate":60,"max_hr_formula":"fox"} → {"max_heart_rate":180,"method":"karvonen"}

GET https://tttkmbb.com/api/v1/calculate/heart-rate-zones?age_years=30

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/heart-rate-zones (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/heart-rate-zones · Markdown: https://tttkmbb.com/health/heart-rate-zones.md · JSON definition: https://tttkmbb.com/health/heart-rate-zones.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="heart-rate-zones"
OpenAPI operationId: calculate_heart_rate_zones
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Why use Karvonen?

It scales zones by heart-rate reserve (max − resting), so fitter people with low resting rates get more realistic targets than a plain percentage of max.

How accurate are age formulas?

Individual maximum heart rate varies by about ±10–12 bpm around any age formula. A supervised maximal test gives the real value.

Related calculators

Running Pace Calculator — Pair heart-rate zones with pace targets.