If you're new to furnace filters, don't worry—we've got you covered. This simple guide will help you understand the basics, including how to choose the right thickness, pick the best MERV rating, and know when it's time to change your filter. Each section links to a deeper resource if you want to learn more.

1. Understanding Filter Dimensions

Furnace filters are sized using three measurements: width × height × thickness—and the last number is the thickness. For example, a filter labeled 16x25x1 is 16 inches wide, 25 inches tall, and 1 inch thick.

These dimensions are specific to your HVAC system. Always check the size listed on your current filter or consult your system’s manual. Choosing the wrong size can reduce airflow and filtration performance.

2. Choosing the Right Filter Thickness

Filter thickness determines how much air a filter can clean and how long it lasts. Thicker filters tend to last longer and hold more dust, but not every HVAC system can fit them.

• 1-Inch Filters: Most common, affordable, and easy to replace. Best for homes with standard air quality needs.

• 2-Inch Filters: Offer better filtration and last longer than 1-inch.

• 4 & 5-Inch Filters: Best for high-efficiency systems and homeowners wanting top-tier air quality with less maintenance.

See our full guide on how to choose the right filter thickness

3. Understanding MERV Ratings

MERV (Minimum Efficiency Reporting Value) tells you how well a filter catches particles.

• MERV 8: Basic protection from dust and pollen. Great for homes without pets or allergies.

• MERV 11: Enhanced protection from smaller particles like pet dander and fine dust.

• MERV 13: Maximum protection from smoke, bacteria, and allergens. Ideal for allergy sufferers and those with respiratory issues.

See our full guide on how to pick a MERV rating that's right for you

4. When to Change Your Filter

How often you should change your filter depends on both its thickness and MERV rating. For example, a 1-inch MERV 13 filter might need to be changed monthly, while a 5-inch MERV 8 filter could last six months.

See our full guide on how often to change your filter

Get Personalized Reminders

Want help remembering when to change your filter? Sign up for our personalized reminder service. Just answer a few quick questions and we’ll send you a schedule tailored to your home and lifestyle.

With this guide, you're ready to make informed decisions and breathe cleaner air every day!