HVAC Filter Size Calculator
Find the standard filter size and MERV rating recommendation based on duct dimensions.
How to Use the Filter Size Calculator
- Measure the duct opening width in inches.
- Measure the duct opening height in inches.
- Click Calculate for standard filter size and MERV recommendation.
Casos de Uso
- •Replacing a lost or unknown filter size.
- •New HVAC installation.
- •Improving indoor air quality.
- •Allergy reduction planning.
Fórmula
Filter size = nearest standard size ≥ duct dimensions. MERV: small ducts→8, medium→11, large→13.
Perguntas Frequentes
What is a MERV rating?
Minimum Efficiency Reporting Value — higher MERV captures smaller particles. MERV 8: basic. MERV 11: allergens. MERV 13: fine particles.
Can I use a higher MERV than recommended?
Higher MERV filters restrict airflow more. Always check your HVAC system's maximum MERV rating before upgrading.
How often should filters be replaced?
MERV 8: every 1–3 months. MERV 11–13: every 3–6 months depending on usage and air quality.