The most accurate way to measure an air conditioner filter is to locate the measurements listed directly on the filter's side panels.
You do not typically need a tape measure to determine the correct size for a replacement filter. Air conditioner filters have their dimensions printed on the frame for easy identification.
Finding Filter Measurements on the Panel
According to the provided reference, you should:
- Locate the measurements listed on the side panels of the filter.
- Note the dimensions starting with the width, then the length, and finally the depth.
- Most filters will actually see two sets of measurements.
- One set is often in large print. This is typically the nominal size (rounded).
- There might be another set, often in smaller print, which represents the actual dimensions.
Always use the measurements printed on the filter itself when purchasing a replacement to ensure a proper fit.
Understanding Filter Dimensions
Air filters are commonly described by three key dimensions:
- Width: The first number listed.
- Length: The second number listed.
- Depth (or Thickness): The third number listed.
These are usually presented in inches, for example, 20x25x1 or 16x20x4.
| Dimension | Description | Typical Placement in Listing |
|---|---|---|
| Width | Side-to-side | First |
| Length | Top-to-bottom | Second |
| Depth | Front-to-back | Third |
Nominal vs. Actual Size
As the reference notes, you might see two sets of numbers.
- Nominal Size: This is the rounded, easy-to-remember size (e.g., 20x25x1). This is the size you usually look for on the packaging when buying a new filter.
- Actual Size: This is the precise measurement, which is often slightly smaller than the nominal size to ensure the filter fits easily into the slot (e.g., 19.5" x 24.5" x 0.75").
When buying a filter, use the larger, nominal size listed on your old filter as your guide.
Steps to Identify Your Filter Size
- Remove the old filter from your HVAC system.
- Examine the cardboard or plastic frame around the edge of the filter.
- Look for printed numbers indicating dimensions (e.g., "16x20x1", "20x25x4").
- Note these dimensions down.
- Use these numbers to purchase your replacement filter.
By using the measurements already printed on the filter, you guarantee that you get the correct size for your specific HVAC unit.
