How to Measure Window AC Cover | Get the Right Fit

Measuring a window AC cover requires three dimensions: width (the side without wiring), depth (the side with wiring), and height (from bottom to top of the control panel), plus a 1–2 inch allowance on width and depth.

A cover that doesn’t fit is worse than no cover at all—it traps moisture, blocks airflow, or blows off in the first wind. Getting the right size is straightforward once you know which side is which. Here’s the exact method, plus what to do when your unit falls between standard sizes.

Which Side Gets Measured for Width vs. Depth

The width is the side of the air conditioner without any wiring, piping, or controls. The depth is the side with the wiring and piping—the side that faces outside or where the hoses connect. This distinction matters because the cover needs a specific opening on the depth side for those wires and pipes to pass through, with fasteners that secure around them. Measuring the wrong side is the most common mistake.

The Three Dimensions You Need

Grab a tape measure and a notepad. Measure to the nearest eighth of an inch, not a rounded fraction. Here are the three measurements:

• Width: Measure across the side without wiring and piping—the narrow side of most window units.
• Depth: Measure across the side with wiring and piping—usually the longer side that extends outside.
• Height: Measure from the bottom of the unit straight up to the top of the control panel. For standard covers, the full height to the top of the air conditioner works; for custom covers, stop at the top of the control panel.

Once you have those numbers, add a 1–2 inch allowance to both width and depth. That extra room ensures the cover slides on easily without being tight enough to damage the unit. If your air conditioner is larger than 48 inches in any dimension, the depth allowance should increase to 2 inches.

Standard Sizes vs. Custom Covers

Most covers are sold by physical dimensions in inches, not by cooling capacity in BTUs—though many list a BTU range they fit. If your unit’s measurements don’t match a standard cover size exactly, buy a cover slightly larger in width and depth. A loose fit is fine; a tight fit is not.

For a perfect match, custom cover manufacturers like Coverstore automatically add a 1-inch allowance to width and depth when building the cover. If your air conditioner exceeds 48 inches, they add a 2-inch allowance to the depth. Exterior measurements are typically rounded up, so you don’t need to guess which direction to round.

Material Matching and Common Mistakes

The right fit is meaningless if the material can’t handle your climate. Quilted indoor covers are for draft blocking and light decoration—they won’t survive a snow load. For winter storage or heavy weather, choose ripstop fabric or a full 360-degree cover that encloses the entire unit. The depth side must have an opening for wiring and piping access with usable fasteners.

Throwing a tarp over the wrong measurements is a temporary fix at best. Before you go shopping, browse the top-rated window AC covers to see what dimensions are most common and which models match your measurements.

Actual dimensions vary by manufacturer and model, so always measure your specific unit rather than relying on the model number or BTU rating. The cover’s size is based on physical inches, not cooling capacity, though many covers list a BTU range they fit as a rough guide.