Furnace Filter Calculator
Determine the optimal furnace filter change frequency based on filter type, pets, household size, allergies, and dust levels.
Inputs
Results
Change Every
73 days
How to Use This Calculator
- Select Filter Type (fiberglass, pleated, HEPA, electrostatic) based on your HVAC system's compatibility.
- Enter Number of Pets and Number of Occupants — pets and larger households accelerate filter loading.
- Toggle Allergy Sufferers and set Dust Level to adjust the change interval for your indoor air quality needs.
- Review Change Days — the recommended days between filter replacements for your specific conditions.
- Check MERV Rating to ensure the recommended filter captures the particle sizes relevant to your health concerns.
- Use Annual Cost to compare filter types on a per-year basis and decide on the best filtration level for your budget.
How the result changes with Number of Pets
| Number of Pets | Change Every |
|---|---|
| 1 | 73 days |
| 3.5 | 41 days |
| 6.5 | 26 days |
| 9 | 26 days |
What each input means
- Filter Type
- 0 = Fiberglass (basic), 1 = Pleated (standard), 2 = HEPA (high efficiency).
- Number of Pets
- Dogs and cats that shed dander and fur, which clogs filters faster.
- Number of Occupants
- People living in the home. More occupants means more particulates.
- Allergy Sufferers
- Set to 1 if anyone in the household has allergies or asthma (recommends more frequent changes).
- Dust Level
- General dust level: 0 = Low (newer home, sealed), 1 = Medium (typical), 2 = High (older home, construction nearby).
What each result means
- Change Every
- Recommended number of days between filter changes.
- Changes Per Year
- Total filter replacements needed annually.
- Annual Filter Cost
- Estimated yearly cost for replacement filters.
- Recommended MERV Rating
- Minimum Efficiency Reporting Value recommended for your household conditions.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersFilter Type = 1, Number of Pets = 1, Number of Occupants = 3, Allergy Sufferers = 0 = 5 input(s) provided
- Calculate Change EveryChange Every73 = 73
- Calculate Changes Per YearChanges Per Year5 = 5
- Calculate Annual Filter CostAnnual Filter Cost60 = $60
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