How to Find Your HVAC Filter Size

Finding Your HVAC Filter Size

Knowing your filter size is essential for proper maintenance and air quality. Here's how to find it:

Method 1: Check Your Current Filter

The easiest way is to look at the filter you currently have installed.

1. Turn off your furnace or HVAC system
2. Locate the filter compartment (usually in the basement near the furnace, or in a filter cabinet)
3. Remove the existing filter
4. Look at the frame of the filter — the size is printed on the edge (e.g., 20x25x1, 16x25x4)

Method 2: Check Your Furnace Manual

Your furnace documentation will specify the correct filter size. Look for the model number on your furnace and reference the manual.

Method 3: Measure Physically

If you can't find the size printed, measure the filter dimensions:

• Length (usually first number)
• Width (usually second number)
• Thickness (usually third number)

Common Filter Sizes

The most common residential filter sizes are:

• 16x25x1
• 20x25x1
• 20x25x4
• 20x25x5
• 16x25x4

Pro Tip: Use FilterSize411 to search your HVAC model number and get the exact filter size needed for your system.

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