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Heating Degree Days (7-Day) Calculator

Σ max(0, base − T_avg) over 7 days.

Compute heating degree-days (HDD) for a 7-day window by summing max(0, base − daily_average_T) across each day. Used by utilities to compare heating-fuel use against weather variability.

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

°F
°F
°F
°F
°F
°F
°F
°F

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

HDD = Σ max(0, base − T_i); classic base = 65 °F.

In depth

Compute heating degree-days (HDD) for a 7-day window by summing max(0, base − daily_average_T) across each day. Used by utilities to compare heating-fuel use against weather variability.