Target Heart Rate Calculator
Jenzzy computes Karvonen zones for fat burn, cardio, and peak effort using max and reserve heart rate.
Inputs
Results
Enter values to see results.
Formula
Target = ((Max − Rest) × %Intensity) + Rest
Max HR often estimated as 220 − age; reserve method personalizes with resting HR.
Example
- Max HR: 185 bpm
- Reserve: 123 bpm
- Zone: ≈ 148 bpm= 148 bpm
Result: 70% zone ≈ 148 bpm
Frequently Asked Questions
220 − age accurate?
Individual max varies—lab tests are gold standard.
Medications?
Beta blockers lower HR response.
Wearables?
Use chest straps for interval accuracy when possible.