How to Measure Your Windows for Custom Shades

Getting the measurement right is the single most important step in ordering custom window shades. A shade that is a quarter-inch too wide will bind against the frame. A shade that is a quarter-inch too narrow will let in light gaps on both sides. Custom shades are made to your exact specifications and cannot be returned once ordered, so accurate measurement matters before anything else.

The first decision is whether you want an inside mount or an outside mount. An inside mount shade sits within the window frame, giving a clean, recessed look that lets the window trim remain visible. An outside mount shade is installed above and outside the frame, covering the trim and typically providing better light blockage. Inside mounts require a minimum frame depth — usually 2 to 3 inches — for the roller mechanism to fit without protruding. If your window frame is too shallow, an outside mount is the better choice.

For an inside mount, measure the width of the window opening at three points: near the top, in the middle, and near the bottom. Windows are rarely perfectly square, so these measurements may differ slightly. Use the narrowest measurement and deduct a small amount — typically 1/4 to 1/2 inch — to allow the shade to move freely without rubbing against the frame. Measure the height from the top of the opening to the sill at three points as well, and use the longest measurement so the shade covers the full opening when lowered.

For an outside mount, measure the width of the area you want the shade to cover. Most installers recommend adding 2 to 3 inches on each side of the window frame to minimize light gaps and provide adequate mounting surface. The height should be measured from where you plan to mount the bracket — typically 2 to 4 inches above the window frame — down to where you want the shade to end, usually at the sill or 2 to 3 inches below it. Outside mount shades are ordered to the exact finished size you specify, with no deductions.

A few common mistakes are worth knowing before you start. First, do not measure the existing shade or blind — measure the window opening itself. Existing treatments may have been ordered incorrectly or may be a different mount type. Second, use a metal tape measure rather than a fabric tape, which can stretch and give inaccurate readings. Third, measure in inches and record fractions to the nearest 1/8 inch — rounding to the nearest inch will result in a shade that does not fit correctly. Fourth, measure each window individually even if they appear identical — windows in the same room often have slightly different dimensions.

Specialty windows require additional care. Arched windows, bay windows, and windows with angled tops need templates or precise angle measurements that go beyond a standard tape measure. Skylights and roof windows require measurements of the actual glass opening, not the surrounding frame. For these situations, a professional measurement visit is the most reliable approach — Beacon Blinds measures every window during the free in-home consultation and handles the order specifications so the shades arrive ready to install.

If you are not confident in your measurements, or if you have specialty windows, hard-to-reach openings, or a large number of windows to measure, a professional measurement visit is worth the time. Beacon Blinds offers free in-home consultations across Austin, Round Rock, Cedar Park, Georgetown, and the surrounding Hill Country. We bring fabric samples, measure every window, and provide a clear quote — no pressure, no fake deadlines. Call (512) 930-1188 or schedule online to get started.