How often should you change your air filter?

Swap when the filter starts catching less and slowing your air. The rule of thumb for a 1" filter is every 3 months for MERV 8 and 11, and about every 10 weeks for MERV 13, which fills faster because it catches finer particles. Thicker 4" and 5" filters usually last 6 months or more.

That rule assumes every month is average. Months when your heat or AC runs a lot fill a filter faster, and so do pollen season, smoke and pets. Here's what fills your filter.

Change it sooner if

• You have pets, especially ones that shed.
• Someone at home has allergies or asthma.
• There's a renovation, construction dust or wildfire smoke nearby.
• Your system runs a lot, like in a hot summer or a cold winter.

Signs it's time

The filter looks gray or clogged, there's more dust on surfaces than usual, or air from the vents feels weaker. A clogged filter makes your system work harder, so changing it on time also helps it last.

How to never forget

When you order, choose "When you need it." We time each swap to your home's weather, pets and allergies instead of the calendar, and check in before each box, so you can skip or change it with a tap.