Degree Days Calculator
Enter daily high and low temperatures to calculate heating degree days (HDD) and cooling degree days (CDD) for energy use estimation.
Settings
Standard: 65°F / 18°C
Daily Temperatures
Load sample week:
Total HDD
0
Heating Degree Days
Total CDD
0
Cooling Degree Days
Days entered: 0
Base: 65°F
Avg mean: —
Daily Log
Add days using the form on the left| # | High | Low | Mean | HDD | CDD | Del |
|---|---|---|---|---|---|---|
| No data yet | ||||||
Interpretation
Summary
Enter daily high and low temperatures to calculate heating degree days (HDD) and cooling degree days (CDD) for energy use estimation.
How it works
- Enter a base temperature (default 65°F / 18°C) — the threshold below which heating is needed and above which cooling is needed.
- Add daily temperature records by entering the high and low temperature for each day.
- The calculator computes the mean daily temperature as (high + low) / 2.
- HDD for a day = max(0, base − mean temperature). CDD for a day = max(0, mean temperature − base).
- Totals accumulate across all days entered to give the period HDD and CDD.
- Higher HDD means more heating energy needed; higher CDD means more cooling energy needed.
Use cases
- Estimate seasonal heating and cooling energy costs before moving to a new region.
- Compare energy demand between two locations or two years.
- Size HVAC systems based on local climate data.
- Verify utility bills against expected degree-day-based consumption.
- Academic coursework in thermodynamics, building science, or energy engineering.
- Track year-over-year climate trends for a building energy audit.
Frequently Asked Questions
Last updated: 2026-06-10 ·
Reviewed by Nham Vu