How often should you change your furnace filter?

A common rule: every 1–3 months for a standard 1-inch filter; thicker 4–5 inch media filters often last 6–12 months. Change it sooner with pets, allergies or heavy dust, and always follow your manufacturer's guidance.

Finding the size: it's printed on the edge of the current filter (for example 16x25x1). Photograph it before you shop.

Yearly service: a technician check before heating or cooling season can catch issues early, especially on older systems.