Furnace Filters – Clean Air for Your Home

At All Filters, we make it easy to find the right filters for your air conditioner or furnace. Whether you need a standard or custom size that’s compatible with your system, our large selection of furnace and AC filters will ensure you find the ideal option. Choose from OEM branded filters or our more affordable alternative, SpiroPure, for the same fit and function. SpiroPure is available in Minimum Efficiency Reporting Value (MERV) 8, 10, 11, and 13. Plus, we stock furnace filters for geothermal, oil, propane, electric, and gas furnace air filter options.

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Select the dimensions of your AC or furnace filter. *If you are looking for a 3”-6” thick whole house air cleaner filter replacement, please browse by brand below rather than using this search feature, as nominal dimension can differ depending on the filter brand.

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How to Choose the Right Furnace Filter

Selecting the ideal furnace filter involves the size, MERV rating, and, in some instances, system compatibility. First, measure your existing filter or check your furnace documentation for the nominal size. Common dimensions include 16x20x1, 20x25x1, and 16x25x1. Note that nominal sizes (the rounded measurements) differ slightly from actual dimensions. Second, consider MERV ratings ranging. A MERV 8 air filter handle basic dust and pollen for most homes, MERV 11 air filters add pet dander and mold spore removal, while MERV 13 provides superior filtration for increased allergen concerns. However, higher MERV ratings increase airflow resistance. Consult your furnace manufacturer's specifications before upgrading to a MERV 13 air filter or higher. Note that geothermal systems may require specialized options or sizes. Browse our complete selection organized by size, type, and brand to find your perfect match.

Furnace Filter Replacement Guide

Replace 1-inch and 2-inch furnace filters every 2–3 months for optimal performance. Homes with pets, allergies, or high dust levels need monthly replacement. Thicker 4-inch pleated or whole-house air cleaner filters last 6–12 months. Replace filters more frequently during peak heating season when your furnace runs continuously. Signs you need immediate replacement include reduced airflow from vents, increased heating bills, excessive dust accumulation, musty odors, or visible dirt on the filter surface. To replace your filter, turn off your furnace, locate the filter slot in the return air duct or air handler, note the airflow direction arrows, remove the old filter, and slide in the new one ensuring arrows point toward the blower. Always maintain a snug fit to prevent air bypass around the filter edges. Measure carefully before ordering as sizes may be made to order and non-returnable.

Get the Best Furnace Filters for Your Home Today

All Filters makes finding the right replacement filter for furnace maintenance simple with our size selector tool, brand directory, and expert customer support available seven days a week. We offer free shipping on all orders over $99 plus Super Value shipping deals on select products. Stock up with multi-pack options for year-round savings and set email reminders so you never forget replacement schedules. Whether you choose premium OEM brands or our cost-effective SpiroPure alternatives, you're guaranteed quality filters delivered quickly. Order online today and breathe easier knowing your home's air quality is protected.

High-Quality Replacement Filters

We stock various filter types and sizes to fit different systems, ensuring you can find the right product that is compatible with your particular make and model. Our high-quality products are designed with advanced filtration technology that effectively captures airborne contaminants, improving indoor air quality. From basic dust filtration to high-performance allergen removal, the products at All Filters are available in a range of MERV ratings to balance efficiency and airflow.

Where Can I Buy High-Quality Air Filters in Specific Sizes?

All Filters stocks one of the broadest furnace filter size inventories available online, covering standard dimensions as well as the less common sizes that big-box retailers rarely carry. Whether your HVAC system takes a popular 16x25x1, a less common fractional size like a 17.5x23.5x1, or something custom, you can search by exact dimension and find a match. Every size ships with the same quality MERV 8, 11, or 13 media, brand-name and SpiroPure compatible options, and SpiroPure multi-packs that reduce per-filter cost over one-off purchases at the store. If you haven't been able to find your size locally, you'll find it here.

Where can I buy high-quality accordion air filters online?

Accordion-style air filters are the high-capacity replacements used in whole-house air cleaners like Space-Gard, Aprilaire, and Carrier Infinity systems. Because these filters aren't stocked at many hardware stores, homeowners often struggle to find the right replacement on short notice. All Filters stocks a range of OEM accordion media filters and select deep-pleat SpiroPure alternatives organized by system compatibility, so you can locate the correct replacement for your air cleaner without guesswork.

Order AC & Furnace Filters Online

The team at All Filters is dedicated to customer support and helping you find air conditioner filters that are compatible with your model. If you’re unable to find your filter or need further assistance, don’t hesitate to call us or chat with us on Live Help. We offer free shipping on all orders over $99, along with special shipping offers for each product. Order online today and get the right filter delivered to your door quickly and conveniently.

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FAQs on Furnace Filters

How often should I replace my furnace filter replacement?

Replace standard 1-inch furnace filters every 2–3 months. Homes with pets or allergies need monthly replacement. Thicker 4-inch pleated filters last 6–12 months. Replace filters more frequently during winter when your furnace runs continuously. Check filters monthly and replace when visibly dirty regardless of time elapsed. Consistent replacement protects your furnace and maintains air quality.

What MERV rating should I choose for my furnace air filter?

MERV 8 filters work for most homes, capturing dust and pollen effectively. MERV 11 adds pet dander and mold spore removal, ideal for allergy sufferers. MERV 13 provides upgraded filtration removing fine particles and smoke. However, check your furnace manufacturer's recommendations. Filters above MERV 11 may restrict airflow in older systems, reducing efficiency and damaging components.

Why is furnace air filter replacement important for improving indoor air quality?

Furnace filters continuously remove airborne particles including dust, pollen, pet dander, mold spores, and smoke from circulating air. Without regular replacement, saturated filters can't capture new contaminants, allowing pollutants to recirculate through your home. This is especially important for family members with allergies or respiratory conditions.

Are reusable or washable furnace filters better than disposable furnace air filters?

Disposable filters typically provide superior filtration and convenience. Washable filters seem economical but require monthly cleaning, proper drying to prevent mold growth, and often carry lower MERV ratings. Washing can damage filter media reducing effectiveness. For most homeowners, the minimal cost of disposable filters outweighs the maintenance hassle and reduced performance of washable options.

What size furnace filter replacement do I need for my system?

Check your current filter's printed dimensions or measure it directly. Note that nominal sizes (rounded measurements like 16x20x1) differ from actual dimensions. Your furnace documentation also lists the required size. Common sizes include 16x20x1, 20x25x1, 16x25x1, and 14x25x1. Get out a tape measure if you're not sure, and measure twice before ordering.

MERV stands for Minimum Efficiency Reporting Values and is an industry-created standard that evaluates the efficiency of air filters. The MERV rating of any particular air filter ranges on a scale of 1 to 16, with a filter rating 1 being the least efficient and a filter rating 16 being the most efficient.
While it is important for the quality of the air in your environment to choose the most efficient filter possible, it is not always as simple as buying a filter with the highest MERV rating. Because the pores allowing for air flow in a highly-rated MERV filter are very small, the filter creates more resistance against air flow and may put too much pressure on the fan of your furnace, air conditioning, or air cleaner unit. It’s important to choose an air filter with the highest MERV rating that your particular unit will allow for maximum air flow. Information about specific MERV ratings and recommendations will generally be included with the documentation that came with your system.
We recommend choosing an air filter with a MERV rating between 8 and 11 for most residential units in order to adequately remove airborne contaminants. If your system can handle a filter with a higher MERV rating, you may wish to use a filter with a rating of 13 for even greater contaminant removal. However, it’s important to remember that filters with a higher MERV rating must be replaced regularly (every 3 months for 1" filters and every 6-12 months for 3- 6" box-type filters) to avoid restricted air flow and negative effects on your system’s performance.

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