How to Measure for Blinds and Shades the Right Way — Avoid Costly Mistakes

Failing to have a fit of a new blind or shade is not due to poor quality: it is due to an incorrect measurement. Even a quarter of an inch can be the difference between the blind that clashes with the frame, leaves gaps on the sides, or does not even fit.

Good news here is that it is very easy to measure windows to install blinds and shades once you understand the two choices you have to make first; inside mount and outside mount and width and height rule. Once you have those two things sorted out, the rest comes within minutes.

This tutorial will show you how to actually measure the windows to fit the blinds and shades, step-by-step, on both types of mount, the roller shades, Roman shades, cellular shades, and faux wood blinds. It also includes the bay windows, the common mistakes, and the cases where a professional is required.

Inside Mount vs Outside Mount Blinds and Shades — What Is the Difference?

Inside mount blinds and shades are installed inside the window frame and gives a clean and built-in appearance that accentuates the frame and the trim. Outside mount shades and blinds are mounted outside and above the window frame on the wall surrounding it, covering much of the window to get more control over the light, and to make the windows look larger.

The first decision you have to make before you have measured anything is which type of mount you would like. This is a difference in the measurement you do, numbers you write and in what order.

The more architectural appearance is provided by the inside mount. It demands that your window frame should be deep, at least 3/4 inch, and preferably 2 inches or more, to receive the headrail and brackets of mounting. Most vinyl-frame windows, standard casement windows and the majority of the double-hung windows have a sufficient depth to mount on the inside.

Outside mount is preferable where the frame of your window is shallow (less than 3/4 inch deep), where the maximum amount of light will be shut out and privacy guaranteed, where you wish to conceal an unsightly or dilapidated frame, or where you wish to make your window look taller and wider than it is.

Always take the doubtful side, and give a measurement. During the free in-home consultation, BuyHomeBlinds.com can tell you which is right to use on which window.

What You Need Before You Start

You will require a steel tape measure (not cloth tape, steel is straiter and more precise), a pencil, a notepad or phone where you can write the readings on and a step ladder, in case any of the windows are too high. Never take an old blind as a measuring guide, blinds fade and misshapen after they grow old.

Tools list:

• Steel tape measure (measures to the nearest 1/8 inch)
• Pencil and notepad or phone
• Step ladder for high windows
• Level (optional – good to check whether a window frame is square or not)

To measure inside mount blinds and shades: come to the top, in the middle, at the bottom, and measure the narrowest point. Three heights (left, centre, right) are measured and the longest measure is taken. No deductions to make – the factory automatically compensates the clearance in case you are ordering custom blinds.

How to Measure for Inside Mount Blinds and Shades

For inside mount blinds and shades: measure the width at three points (top, middle, bottom) and record the narrowest measurement. Measure the height at three points (left, centre, right) and record the longest measurement. Do not make deductions — the factory automatically adjusts for clearance when you order custom blinds.

Step 1 — Check the depth first

Measure depth of the frame of the window- before measuring width or height, take depth of the frame- distance between the glass and outer edge of frame. The depth required will depend on the product: the vast majority of faux wood blinds require at least 23/4 inches, cellular shades require at least 2 inches and roller shades require at least 2 inches. In case of a frame which is too shallow, use an outside mount.

Step 2 — Measure the width

Insert your steel tape measure in the casing of the window. Measuring the width measure at three points, i.e. top, middle and bottom. Record all three numbers. Wrap around the slimmest size – the size you place an order.

Step 3 — Measure the height

Measuring the height in the frame measures at three places; left side, centre, and right side. Distance between the frame and the sill of the window. Record all three numbers. Measure the longest length – this is the height that you place when making an order.

Step 4 — Check for obstructions

Measuring the height in the frame measures at three places; left side, centre, and right side. Distance between the frame and the sill of the window. Record all three numbers. Measure the longest length – this is the height that you place when making an order.

Step 5 — Check if the window is square

Measure the window diagonally -that is, the top left corner to bottom right, the top right to bottom left. When the two diagonals measure more than 1/2 inch apart, then the window is out of square. In the case of out-of-square windows, an outside mount is suggested to best fit the window.

• Note To Roller Shades: The roller shade width is approximately a little less than the shade width (excluding the roller tube) of the shade. Inside mount roller shade measures- inside measures are exactly the same as above, the factory will take this difference into consideration automatically.
• Note For Roman Shades: Roman mount on the inside are also measured in the same manner- narrowest width, longest height. Roman shades are usually constructed 1/2 inch smaller than the actual dimension in order to enable the fabric to be stacked neatly when raised.
• Note For Cellular Shades: Cellular shades are measured exactly as above. Confirm minimum depth: single-cell shades need 2 inches minimum, double-cell shades need 2½ inches minimum.

How to Measure for Outside Mount Blinds and Shades

In the case of outside mount blinds and shades: you need to determine where you want to position the headrail, how many inches in all you wish to cover, both sides of the frame, and how many inches in all you want the blind to go down to. Note the full width and height make sure you do not deduct.

Step 1 — Mark the headrail position

Choose the height of the mounting of the blind above the window frame. The mounting of most outside mount blinds is 2 to 4 inches above the top of the frame – higher mounting will cause the window to be taller. Make a light pencil mark on this point. Make sure that at this point there must be a minimum of 2 inches of flat wall or trim to mount the brackets into.

Step 2 — Measure the width

Measure the width that you desire the blind to cover (all the way around) starting and ending outside the window frame on both sides. Attach at least 2 to 3 inches (4 to 6 inches) all around (and not less) the frame edge to create minimum light gaps and cover the whole frame. As an illustration: an outside mount blind would have to be at least 42 to 48 inches wide to fit into a window frame 36 inches in width. Bear this total width down to the record.

Step 3 — Measure the height

Using a pencil, measure downward (where you wish the blind to finish) where the headrail mounting point is – normally to the window sill, or 1 to 2 inches below the sill to give full coverage. In the event that the window lacks sill, then measure to the floor or to your drop point of choice. Note this height in total.

Step 4 — Check for obstructions

Find the door handles, deadbolts, light switches or moulding that sticks out of the wall around the window. These are capable of blocking outside mounted blinds. The blind can be lengthened with extensions brackets or spacer blocks in case necessary – be aware of any hindrances when placing an order.

How to Measure Bay Windows and Awkward Shapes for Blinds and Shades

In the case of bay windows, each part of the bay is a separate window which is measured. The widths of the panels are likely to be different. Measure each panel separately – do not suppose two are alike. The minimum interior mount depth, in the case of arched windows, is 11/2 inches. They are mostly bottom-mounted shades on arched windows alone – call BuyHomeBlinds.com about arched window specialists.

• Bay windows: treat each angled section as its own separate window. Record the width and height of each panel by following the above steps of using the inside or outside mounts. Sample each section separately as a blind or shade – do not attempt to make a complete bay of one product.
• Arched windows: inside mount is possible with a minimum frame depth of 1½ inches. Majority of the arch treatments are bottom-only. When you wish to put an arch shade on top of another treatment, you should plan where both headrails are going to be located, and then measure either of them.
• Out-of-square windows: if diagonal measurements differ by more than ½ inch, outside mount is the recommended approach. Out-of-square window will reveal visible gaps at the edges of the frame with inside mount blinds.

Measuring for Specific Blind and Shade Types

Measuring for Faux Wood Blinds

Installation Measure correctly as required above and install on inside or outside. Inside mount Minimum depth of faux wood blinds in 2-inch 23/4-inch. The depth requirement needed in cordless faux wood blinds is a little bit more – refer to the page of the product. On frames that are slightly uneven, faux wood is the most lenient material to use because it is rigid.

Measuring for Roller Shades

Inside mount roller shades: They use the narrowest width and largest height as above. The roller tube will also increase the depth of your total by about 3/4 inch of roller tube – be sure that your frame is at least 2 inches deep. Outside mount roller screens: increase 2 or 3 inches on either side of the frame width. The frame will be covered with fabric and the roller tube will be placed on the frame.

Measuring for Roman Shades

Internally mounted: smallest width and tallest height. The Roman shades are usually prepared one-half inch less than the actual width. External mount: increase by 2 to 3 inches on each side. When Roman shades are lifted, they assume horizontal folds, which the shades assume after being pulled up, leave the shade enough above the window when it is completely open (about 8 to 12 inches with the window height of most windows).

Measuring for Cellular Shades

Internal mount: thinnest width, tallest height. Check depth (2 to 21/2 inches minimum according to cell type). The product that is the most depth-sensitive is cellular shades. When your window is at the edge as to depth, the outside mount will be a cleaner look and no decrease in performance will be seen.

The Most Common Measuring Mistakes — and How to Avoid Them

Most 5 famous measuring errors include: measuring once at a single point (measure at three points always), measuring with cloth tape measure instead of steel, writing down measurements on a blind that is already in the window, forgetting to measure depth of the frame where it is to be mounted, and not factoring in obstructions such as handles or locks within the frame.

Mistake 1 — Measuring in only one place

Windows are not very often square. Always measure width at the top, middle and bottom. Measure height at all times at left, centre and right. The speediest path to a blind that binds or gaps is by the use of a single measurement.

Mistake 2 — Using a cloth or retractable cloth tape

Cloth tapes are slack and loose and do not provide correct measurements of large windows. A stiff steel tape measure should be used always.

Mistake 3 — Ordering based on an existing blind’s size

The old blinds wither, distort, and were not too sure to be inaccurately gauged at the outset. It is a good idea to measure the window rather than the blind already there.

Mistake 4 — Forgetting to check depth for inside mount

Made as an inside mount blind, which is ordered to fit a frame too shallow, cannot be completely recessed, will stick out at the wall, and look incomplete. Measure nothing until the check depth is made.

Mistake 5 — Ignoring obstructions

Inside-mounted blinds can be prevented to be used by window cranks, handles, locks, and triming that protrude out of the frame. Obstruction Check Before ordering, check for obstructions and note them.

Final Thoughts

Getting your measurements right is the most important step in buying blinds and shades that look good, fit perfectly, and last for years. Follow the steps above for inside and outside mount, measure every window individually, always use a steel tape measure, and double-check every figure before you order.