Air Filter Replacement Calculator Formula
Understand the math behind the air filter replacement calculator. Each variable explained with a worked example.
Formulas Used
Replace Every
replacement_days = round(adjusted_life)Filters per Year
annual_filters = ceil(365 / adjusted_life)Annual Filter Cost
annual_cost = ceil(365 / adjusted_life) * filter_costVariables
| Variable | Description | Default |
|---|---|---|
filter_life_days | Rated Filter Life(days) | 90 |
pets | Number of Pets | 1 |
allergy_household | Allergies in Household (0=no, 1=yes) | 0 |
filter_cost | Cost per Filter(USD) | 15 |
adjusted_life | Derived value= filter_life_days * max(1 - pets * 0.15 - allergy_household * 0.2, 0.3) | calculated |
How It Works
HVAC Air Filter Replacement
Air filters trap dust, pollen, and pet dander. Replacing them on time maintains air quality and HVAC efficiency.
Adjusted Replacement Interval
Adjusted Life = Rated Life x (1 - Pet Factor - Allergy Factor)
Each pet reduces filter life by about 15%, and allergy concerns warrant replacing 20% sooner. A clogged filter reduces airflow, increases energy costs by 5-15%, and can damage the HVAC system.
Worked Example
A 90-day rated filter in a home with 1 pet and no allergies, costing $15 each.
filter_life_days = 90pets = 1allergy_household = 0filter_cost = 15
- 01Adjusted life = 90 x (1 - 0.15 - 0) = 90 x 0.85 = 76.5 days
- 02Rounded = 77 days
- 03Filters per year = ceil(365 / 76.5) = 5 filters
- 04Annual cost = 5 x $15 = $75
Ready to run the numbers?
Open Air Filter Replacement Calculator