How does the Degree Days Calculator work?

Heating degree days (HDD) = sum of (65 - daily avg temp) for days below 65°F Then: Cooling degree days (CDD) = sum of (daily avg - 65) for days above 65°F Then: Higher values indicate greater heating/cooling needs.

Can you give an example of how to use the Degree Days Calculator?

Example: Input City: 5000 HDD/year (cold climate), another 1000 (warm) gives a result of Cold climate needs 5× more heating, affecting system size and fuel use (Major design driver).

Is the Degree Days Calculator free to use?

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

How accurate is the Degree Days Calculator?

Our Degree Days Calculator uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.

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Degree Days Calculator

Average Temperature (°C)

Base Temperature (°C)

Number of Days

Heating and cooling degree days quantify heating/cooling needs based on temperature deviation from base (usually 65°F/18°C).

Symbol	Name	Unit	Description
HDD	sum of (65 - daily avg temp) for days below 65°F	—	sum of (65 - daily avg temp) for days below 65°F
F	F value	—	Variable used in the calculation

Difficulty:beginner

References

›Degree Days — Wikipedia

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Degree Days Calculator

Degree Days Calculator

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Degree Days Calculator