Explain that outside mount blinds are measured according to the total area the homeowner wants to cover, rather than only the inside window opening. The user must decide where the headrail will sit, measure the desired width and height, and include enough overlap around the window for privacy and light control.
Mention that outside-mounted blinds are usually made to the exact dimensions submitted, so the homeowner must include the desired overlap in the measurements. Blinds.com and The Home Depot both emphasize measuring the full area to be covered and allowing additional space for the headrail and side coverage.
What Are Outside Mount Blinds?
Explain that outside mount blinds are installed on the wall, ceiling, or window trim outside the window opening.
Unlike inside mount blinds, they do not need to fit within the recess. This makes them useful for shallow, uneven, or obstructed window frames.
Briefly explain that outside mounts can also:
- Cover unattractive or uneven trim
- Reduce visible side light gaps
- Make a window appear wider or taller
- Provide more privacy
- Work where there is not enough inside mounting depth
Keep this section mostly paragraph-based.
What You Need Before Measuring
Explain that the reader needs a steel tape measure, pencil, paper or phone, and a step ladder when necessary.
Advise the reader to measure to the nearest 1/8 inch and use the same measurement format throughout the project.
Explain that a steel tape measure is more accurate than a soft cloth tape because it remains straight and does not stretch.
Decide Where the Blind Will Be Mounted
This section should appear before the measuring steps because outside mount dimensions depend on the exact mounting position.
Wall Mount
Explain that the brackets are installed on the wall above and beside the window trim. The reader must check that enough flat wall space is available for the brackets.
Trim Mount
Explain that brackets may sometimes be installed directly on flat window trim. The trim must be wide, strong, and level enough to support the blind.
Ceiling Mount
Explain that blinds may be mounted to the ceiling when there is limited wall space above the window or when the homeowner wants a floor-to-ceiling appearance.
Tell the reader to decide on the mounting location before recording the final width and height.
Check for Space and Obstructions
Explain that the user should inspect the area around the window before measuring.
The headrail and brackets need a flat mounting surface. Decorative molding, uneven trim, door handles, window cranks, deadbolts, vents, cabinets, or nearby walls may affect the available space.
The Home Depot specifically recommends making allowances for obstructions such as molding and door hardware when measuring an outside mount.
Check the Space Above the Window
Explain that the reader should check the height of the headrail and brackets before choosing the top mounting point.
Many guides recommend allowing extra space above the frame for mounting hardware, but the exact amount should follow the selected product’s specifications. Blinds.com, for example, recommends beginning at least three inches above the frame for many traditional blinds and shades.
Check How Far the Blind Must Project
Explain that handles, trim, or sills may require spacer blocks or extension brackets to move the blind farther away from the wall.
The blind must clear all obstructions while raising and lowering.
How to Measure Windows for Outside Mount Blinds
This should be the main section of the article.
Step 1 — Label Each Window
Explain that every window should have a clear label, such as “Living Room Left” or “Primary Bedroom.”
Even similar-looking windows should be measured separately.
Step 2 — Choose the Top Mounting Point
Tell the reader to decide exactly where the top of the headrail will sit.
The top position must provide enough room for brackets and should be level across the window.
If the homeowner wants the window to look taller, the blind may be mounted higher. However, the selected blind must still be long enough to cover the window and reach the desired bottom point.
Step 3 — Measure the Window Width
Explain that the user should measure the width of the window opening or trim, depending on what they want the blind to cover.
If the window has trim and the blind will cover it, measure from the outside edge of the left trim to the outside edge of the right trim.
If there is no trim, measure the full window opening from left to right.
Take measurements at the top, middle, and bottom, especially if the frame or trim appears uneven. Use the largest base width before adding the desired overlap.
Step 4 — Add Side Overlap
Explain that outside mount blinds should extend beyond both sides of the window to reduce gaps and improve privacy.
Do not present one overlap as universal. Competitor recommendations vary by product and desired coverage. Blinds.com recommends at least 2½ inches on each side for many traditional outside-mounted blinds, while The Home Depot suggests adding extra coverage around the window for improved privacy and light control.
Include an example:
Window opening width: 40 inches
Left overlap: 2 inches
Right overlap: 2 inches
Final ordering width: 44 inches
Clarify that the total ordering width includes both side overlaps.
Step 5 — Measure the Height
Tell the reader to measure from the chosen top mounting point to the desired bottom point.
If the window has a protruding sill, the blind may end at the sill.
If the window has no protruding sill, the blind can extend below the opening for better coverage. Blinds.com recommends measuring below the sill when possible, while The Home Depot suggests allowing additional height for coverage and mounting hardware.
Step 6 — Add Top and Bottom Overlap
Explain that the reader must include enough space above the window for the headrail and brackets.
The bottom overlap depends on the sill and the desired coverage. A blind mounted above the frame and extending below the window can reduce light leakage and make the window appear taller.
Include an example:
Window opening height: 60 inches
Top allowance: 3 inches
Bottom allowance: 2 inches
Final ordering height: 65 inches
Step 7 — Record the Final Size
Explain that outside mount measurements are recorded as:
Width × Height
Example:
44 inches W × 65 inches H
Clarify that this should be the complete finished coverage size, not only the original window-opening size.
Will the Manufacturer Make a Deduction?
Give the answer immediately:
Outside mount blinds are generally made to the exact width and height submitted, so the customer must include all desired overlap in the order size.
This differs from many inside mount products, where the manufacturer may make a small factory deduction.
Blinds.com states that its traditional outside-mounted treatments are made to the exact submitted measurements without factory adjustments.
Advise readers to review the exact product instructions because ordering practices can vary between suppliers.
How Much Overlap Do Outside Mount Blinds Need?
This section directly answers a high-intent supporting query.
Explain that there is no single overlap that works for every window and blind.
The ideal amount depends on:
- Available wall or trim space
- Blind type
- Window hardware
- Desired privacy
- Desired room darkening
- Decorative trim
- Whether the homeowner wants the window to appear larger
A practical starting point is approximately two to three inches on each side, with enough additional height for the brackets and lower coverage. However, the product guide should always take priority.
For bedrooms or media rooms, more overlap may help reduce side light. For windows close to a wall, cabinet, or door, the available space may limit the overlap.
Should You Measure the Window Opening or the Trim?
Explain that the answer depends on what the blind is intended to cover.
If the blind will cover only the opening, measure the window opening and add the desired overlap.
If the blind will cover the trim, measure from the outside edge of the trim on one side to the outside edge on the other side, then decide whether more overlap is required.
For wide or decorative molding, make sure the brackets have a flat mounting surface. If the trim projects forward, the installation may require spacer blocks or extension brackets.
How to Measure When the Window Has a Sill
Protruding Window Sill
Explain that when the sill projects outward, the blind will often end at the sill. Measure from the selected top mounting point to the top of the sill.
Make sure the blind will clear the sill and hang straight.
Flush or No Window Sill
If the sill does not project outward, the blind can extend below the window opening. This can improve privacy and reduce light gaps.
Tell readers to choose the bottom endpoint before recording the final height.
Measuring Tips for Popular Blind Types
Keep these sections brief and relevant to outside mounting.
Roller and Solar Shades
Explain that outside mounting can reduce the side gaps commonly seen with inside-mounted roller and solar shades.
The final width must include enough overlap for the fabric—not only the brackets or cassette—to cover the opening.
Zebra Shades
Explain that the cassette and fabric width may differ. Readers should check the supplier’s finished fabric width and cassette dimensions before deciding how much overlap to add.
Wood and Faux Wood Blinds
Explain that the headrail and valance may extend beyond the blind slats. The mounting surface must have enough room for the brackets and decorative valance.
Vertical Blinds
Explain that vertical blinds often need additional side and height clearance, especially over sliding glass doors. The vanes should not drag on the floor or sill.
Motorized Blinds
Explain that motorized blinds may need room for a larger cassette, charging access, wiring, battery components, or power connections.
Professional measuring may be helpful for large or expensive motorized treatments.
Common Outside Mount Measuring Mistakes
Write this mainly as natural paragraphs.
Cover these mistakes:
- Measuring only the window opening and forgetting overlap
- Adding overlap to only one side
- Failing to include space for the headrail
- Measuring from the wrong top mounting point
- Ignoring a protruding sill
- Forgetting trim or molding
- Failing to check handles and door hardware
- Assuming the manufacturer will add overlap
- Reversing width and height
- Rounding the measurements
- Measuring one window and applying it to several windows
- Not checking whether the wall or trim is suitable for brackets
End by advising readers to measure twice and confirm the exact product requirements before ordering.
Outside Mount vs Inside Mount Blinds
Use a concise comparison table.
| Feature | Outside Mount | Inside Mount |
| Installation | Wall, ceiling, or trim | Inside window recess |
| Depth required | Usually no | Yes |
| Light coverage | Generally better | Small side gaps more common |
| Shows trim | Usually no | Yes |
| Works with uneven frames | Often | Not always |
| Can make window look larger | Yes | Usually no |
| Factory deduction | Usually none | Often applied by manufacturer |
Explain that outside mount blinds are often better when the frame is shallow or uneven, or when stronger coverage is needed.
Inside mounts work well when the frame is deep, square, and the homeowner wants a clean built-in appearance.
Can You Measure Outside Mount Blinds Yourself?
Explain that homeowners can usually measure simple rectangular windows themselves.
Professional measuring is more useful when dealing with:
- Large windows
- Sliding glass doors
- Motorized blinds
- Floor-to-ceiling windows
- Bay or corner windows
- Decorative or uneven trim
- Concrete or metal mounting surfaces
- Multiple blinds that must align at the same height
Keep this section informative rather than overly promotional.
Conclusion
Summarize the essential process without repeating the entire article.
Explain that successful outside mount measurements depend on choosing the mounting position first, measuring the area to be covered, adding suitable side and vertical overlap, checking for obstructions, and recording the complete finished size as width by height.
Remind the reader that outside mount blinds are generally made to the submitted size, so all overlap must be included before ordering.
Frequently Asked Questions
How do you measure a window for outside mount blinds?
Measure the total area you want the blind to cover, including the desired overlap on both sides and enough space above and below the window.
How much wider should outside mount blinds be?
A common starting point is two to three inches on each side, but the exact overlap depends on the product and available space.
How high should outside mount blinds be installed?
The mounting point must provide enough room for the headrail and brackets. Many products need several inches above the frame, but the product specifications should determine the final position.
Do I measure the window or the trim?
Measure the window opening when the blind will cover the opening only. Measure the outside edges of the trim when the trim will also be covered.
Does the manufacturer add overlap?
Usually not. Outside mount treatments are commonly made to the exact dimensions submitted, so the overlap must be included in the order size.
Should outside mount blinds cover the window sill?
They may end at a protruding sill. If the sill is flush, the blind can extend below the opening for better coverage.
Do I need to measure the window in three places?
It is helpful when the frame or trim is uneven. Use the largest base width before adding overlap.
Can outside mount blinds reduce light gaps?
Yes. Extending the blind beyond the opening can reduce visible gaps and improve room darkening compared with many inside mounts.
Can outside mount blinds make a window look larger?
Yes. Mounting the blind higher and wider than the opening can make the window appear taller and wider.
Should every window be measured separately?
Yes. Even similar-looking windows can have different trim, wall space, and dimensions.
