Inside vs Outside Mount: What Each One Asks of Your Window

You are at the window with a tape measure and the shop’s size box open on your phone, and the question you say out loud is the simple one. Does this go inside the frame, or on the wall over it?

Everyone answers it the same way. Measure the depth of the recess, compare it to the number on the listing, and if it fits, mount inside, because inside is the neat one. Outside is what you do when the recess lets you down.

Six listings from three merchants, read on their own product pages, describe a different choice. Inside vs outside mount turns out to be a light decision wearing a fitting decision’s clothes. One of the two options carries a published warning. The other carries none, and it is the one you would have called the fallback. Choosing between them is one stage of measuring, hanging and installing a window properly, and it is the stage that changes what the other two are for.

Both mounts sit in the same dropdown, and only one of them comes with a warning

Start with what these six agree on. Five offer both mounts in the same ordering step, at the same base price, with nothing to pay either way. The sixth, a hardwood plantation shutter, offers one: “Installation: Inside-mount only.”

They agree on something else nobody repeats. The outside mount has no depth requirement at all. “No minimum depth is required,” says the aluminium venetian listing, and the roller listings say it in other words. A recess two inches deep and a recess ten inches deep are the same window to an outside mount.

In the room

Now read the same pages on the inside mount. The venetian: “Please note that slight side gaps may occur due to the headrail deduction. For enhanced light control and reduced side gaps, consider selecting an outside mount.” The Tavi roller: “Note there will be slight gaps on sides due to fabric deductions. For more light blockage, consider ordering as outside mount.” The linen roman shade at Half Price Drapes: “If the window depth is less than 2 3/4″ we suggest changing to an outside mount.”

Three merchants, working separately, all put their hedge on the same side. The dropdown costs nothing either way, and the only option any of them qualifies is the one everybody takes by default. At noon on a bright day that qualification is a strip of daylight down each side of the recess, on every shade in this set.

What the reveal takes off you, before anyone has held a tape

All six publish a width deduction for the inside mount, and here they stop agreeing: 1/4 inch on the venetian, the cellular and the HPD roman, 3/8 inch on the Tavi and the bamboo, 1/2 inch on the shutter. That fraction sits between the window you measured and the covering that gets made. Which of you is expected to subtract it, and how to write the number the order box is asking for, is its own job.

None of them publishes the second number, the one you actually want: how much window is left uncovered once the shade hangs. A deduction is not a light gap. It comes off before manufacture, and the finished thing can lose more. Nobody prints that figure, so this page does not either.

In the room

On a shade sold for light, the first number is already the story. Two Pages describes the Aura cellular as having “high-density blackout fabric and an aluminum-coated interior that completely blocks light”, and publishes on the same page a deduction and a bracket that put daylight down both sides of the cloth. In an east-facing bedroom in June, at six in the morning, the strip on the jamb is what wakes you.

How much window the ordered width really covers

Two Pages TWOPAGES Veritas Hardwood Plantation Full Height Shutter1/2 in

the factory takes 1/2 in off the width you give

Neutral Curtains Tavi Roller Shades3/8 in

the factory takes 3/8 in off the width you give · outside mount: 2 to 4 in wider than the window frame

Neutral Curtains Custom Bamboo Shades & Blinds – Alum. Headrail3/8 in

the factory takes 3/8 in off the width you give

Two Pages Loma Venetian Blinds Cord Lift1/4 in

you order 1/4 in under the casing width · outside mount: 2 to 4 in more than the window width

Two Pages Aura Blackout Cellular Window Shades Cordless1/4 in

you order 1/4 in under the casing width

Half Price Drapes Crisp White French Linen Roman Shade1/4 in

the factory takes 1/4 in off the width you give · outside mount: at least 1 1/2 in on each side, 3 in total

Two different numbers hide under the same word. A deduction is what you take off the casing before ordering; a light gap is what the finished shade still leaves uncovered afterwards. No listing here publishes the second.

Taken from the official Half Price Drapes, Neutral Curtains, Two Pages product pages on 2026-09-19. We measure nothing ourselves, so every percentage here is the figure the brand prints.

Neutral is blunter about where the leak starts. On the Tavi it notes that the deduction applies to the headrail width, not the fabric width, and that a genuine hundred per cent blackout needs the front valance, because “back valance may let light in from the sides, since the headrail depth is around 2 inches.” The light goes round the top and down the edges, which makes it a mounting problem wearing a fabric problem’s clothes. It is the same reason a blackout roman shade gets its darkness from its edges and its lining, with the face fabric doing the least of the work.

Opacity, as each brand states it

Two Pages says

no opacity figure published

Two Pages says

blackout claimed by the brand, no percentage published

Two Pages says

no opacity figure published

Neutral Curtains says

blackout and light filtering offered as separate options; no percentage published

Neutral Curtains says

no opacity figure published

Half Price Drapes says

depends on the lining chosen

These are manufacturer claims, quoted as published. They are not measurements taken by this site, and the vocabulary is unregulated.

Taken from the official Half Price Drapes, Neutral Curtains, Two Pages product pages on 2026-09-19. We measure nothing ourselves, so every percentage here is the figure the brand prints.

The measurement nobody takes is the flat bit round the edge

So the outside mount needs no depth. It does need something, and Two Pages is the only merchant here that prints it as a line item: minimum outside mount flat space, 1 inch on the Aura cellular, 2 inches on the Loma venetian. Two listings, one shop, two figures, because the brackets are different sizes. The number belongs to the product.

Half Price Drapes asks for the same thing in the language of coverage: a minimum of 1 1/2 inches on each side of the opening, 3 inches in total, and for the height, 2 to 3 inches above the opening to clear the 2-inch wooden mounting board and its hardware. Read together, those are instructions to find a clean band of casing or wall about two inches wide, round three sides of your window.

A measure worth keeping

1 to 3 1/8 in of flat space, depending on the headrail

An outside mount has a measurement too

Depth is the inside-mount question. An outside mount asks a different one: how much flat, uninterrupted casing or wall there is around the opening for the brackets to land on.

The reveal can be two inches deep and the answer is still no, because the architrave is moulded, the wall is tiled to the frame, or a light switch sits four inches to the left. Listings that publish a minimum flat space publish different figures for different headrails on the same shop, so the number belongs to the product, not to the mount. It is the one measurement nobody takes, because the tape has already been put away.

Trade convention and proportion, not something a merchant told us. A tape measure settles it faster than we can.

Go and look at a real window and that band is often missing. A moulded architrave has a flat face an inch wide and then a curve. Tile runs to the frame in a bathroom. A light switch sits four inches to the left. An outside mount gets refused by the wall, and you find that out holding the brackets against the plaster, at the point where you were about to decide what you are screwing into.

Two inches is less than the width of your hand, and nobody measures it, because by the time the mount is decided the tape has been put away.

Inside vs outside mount, read one listing at a time

Read a row end to end and the mount usually picks itself. These are blinds, shades and one shutter, and the pattern holds across all three.

What each mount asks of the window, listing by listing

Listing	Inside the reveal	On the wall or casing	Offered
Two PagesLoma Venetian Blinds Cord Lift	3 in of depth (3 1/8 in flush) · you order 1/4 in narrower	2 in of flat space · add 2 to 4 in more than the window width	both
Two PagesAura Blackout Cellular Window Shades Cordless	2 in of depth (2 1/4 in flush) · you order 1/4 in narrower	1 in of flat space	both
Two PagesTWOPAGES Veritas Hardwood Plantation Full Height Shutter	1 3/4 in of depth · the factory takes 1/2 in off	not offered on this listing	inside only
Neutral CurtainsTavi Roller Shades	3 5/8 in of depth · the factory takes 3/8 in off	add 2 to 4 in wider than the window frame	both
Neutral CurtainsCustom Bamboo Shades & Blinds – Alum. Headrail	the factory takes 3/8 in off	not published	both
Half Price DrapesCrisp White French Linen Roman Shade	2 3/4 in of depth · the factory takes 1/4 in off	add at least 1 1/2 in on each side, 3 in total · extend at least 2 to 3 in above the window opening to clear the 2 in wooden mounting board and hardware	both

5 of these 6 listings offer both mounts, and 2 publish a minimum flat space for the outside one. None of them asks for any depth on the outside mount. Empty cells mean the product page does not publish the figure, never that a neighbouring listing was read instead.

Taken from the official Half Price Drapes, Neutral Curtains, Two Pages product pages on 2026-09-19. We measure nothing ourselves, so every percentage here is the figure the brand prints.

The shutter’s row is the shortest and the most instructive. It asks for the least depth of the six, 1 3/4 inches, a full inch below some of its neighbours, and it is the most rigid object on the page. The rest of its row is blank, because there is no outside option to describe. Depth rules that product in or out, and nothing else about its mount is open.

Compare the two

Taken from the official Half Price Drapes, Two Pages product pages on 2026-09-19. We measure nothing ourselves, so every percentage here is the figure the brand prints.

The answer in the FAQ is not an answer about your shade

Here is the part that costs people money.

Neutral’s product pages carry an FAQ block, and one of its questions is exactly the one you came for: What is The Minimum Depth Requirement For Inside Mounted? The answer runs to two words. “2 inches.”

The same two words appear on three listings. On the Tavi, one of the few roller shades either of these two merchants sells, whose own specification block ten lines higher on the same page asks for “3 5/8 inches minimum depth requirement.” On the Custom Bamboo and the Willow bamboo, neither of which publishes a depth anywhere. That answer is shop-wide copy parked under a product, and all it reliably tells you is that somebody wrote an FAQ once.

Two Pages runs a version of the same trick. The FAQ on its drilled Aura listing answers for the no-drill version of that shade, telling you to “deduct 1/4″ from your measured width yourself”, while the specification block on the page you are reading asks for 3/8. It does slip in one line about outside mounts worth keeping: “For outside mount, no deduction is needed.”

Do the sensible thing, open the FAQ and look for your question, and you order an inside mount for a recess that will not take it. On made-to-measure, that does not go back.

Where this usually goes wrong

The habit	What it costs	Instead
Taking the answer in the FAQ for the specification The depth question is answered twice on the same product page, once in the specification block and once in the FAQ further down, and the FAQ is the one that gets read, because it is written as a sentence.	FAQ blocks are written for a shop, not for a listing. The same two-word answer can sit under a shade whose own specification block asks for nearly twice that depth, and under two more shades that publish no depth at all. Order against it and the covering is bought for a reveal that will not take it, on a made-to-measure order that cannot go back.	Read the specification block, and treat the FAQ as shop-wide copy until proved otherwise. If the two disagree, the stricter figure is the one to measure against, and the gap between them is worth an email before the order, not after.

Where this usually breaks down, and the correction. No product figures are involved.

One shop makes you tick a box, another calls the wrong mount a defect

The three merchants take this decision seriously to three visibly different degrees.

Half Price Drapes, whose roman shades are the only made-to-measure product in this set with a price calculator on the page, holds the cart shut. Above the Add to Cart button sits the line “Please confirm your window depth before adding this item to cart” and a tick box: “I have measured my window depth and agree that it is at least 2 3/4″ deep.” Nothing on the page stops you ticking it without getting up, and it still makes you say the number out loud before you spend the money.

Neutral writes it into its after-sales list instead. Among the faults it will remake, alongside the wrong colour and the wrong size, is “Processing Error: Outside mount made as inside mount?” The size threshold on that list is a discrepancy greater than 3/8 inch, which is the width of its own deduction.

In the room

It is also the only one of the three that lets you switch the deduction off, and it says so plainly on its bamboo listing: “If you are concerned about light gaps, please leave a note with your order requesting no width deduction. If no note is provided, the standard 3/8″ width deduction will be applied by default.” One sentence in the comments box, free, offered by one shop out of three.

A step that pays off

Ask for the deduction to be left off

On a made-to-measure shade where the factory takes a fraction off your width by default, check whether the listing lets you cancel it with a note on the order. At least one merchant says so in writing, and says the default applies if no note is given.

That fraction is the side gap. Cancelling it buys back the light the covering was chosen to stop, and it is free. The trade is a tighter fit: with nothing taken off, a reveal that is out of square or freshly painted can bind, and a shade that rubs is worse than a shade that leaks. Worth it on a bedroom, rarely worth it on a window you open every day.

Method, not merchandise. No part of this changes with where you bought the curtain.

Two Pages says nothing about any of it. It prints the numbers and lets you order.

The window you actually open decides this before the depth does

One more input, and it beats the tape.

Half Price Drapes publishes this one as a disqualification: the window frame “must be free of any obstacles such as cranks” and the window “must not open inwards”, or the listing sends you outside. An inside mount on a window like that has to be raised before the sash will move, every time, so a shade over an inward-opening casement quietly becomes a shade you leave up all summer and a window you stop opening. Mounted outside, the sash swings under it.

In the room

The Aura listing gives away something else in its measuring instructions. For an inside mount, measure the width at the top, middle and bottom and use the narrowest. That instruction exists because recesses go out of true. If your three widths differ, the shade gets built to the tightest one, and the daylight down the two jambs comes out wider on one side than the other. Outside the opening none of that applies: you have stopped measuring a window and started choosing a rectangle.

Another way to do it

Put it on the wall over the window you actually open

On a sash that swings inwards, a casement with a crank, or any window with a handle standing proud of the frame, mount the covering outside the opening even when the reveal is deep enough to take it inside.

At least one merchant publishes this as a disqualification, not a preference: the frame has to be clear of cranks and the window must not open inwards, or the listing sends you to the outside mount. Inside the reveal, the covering has to be raised before the window will move, so a shade over a casement quietly becomes a shade you leave up all summer. Outside, the covering clears the handle and the window opens under it. You lose the frame as a visible detail and you gain a window you still use.

This is a layout idea rather than a purchase. The panels you have will do it.

Which mount, for which window

If light is the reason you are buying, mount outside, even when the recess would take it. Three of these six listings tell you so themselves, and the ones that stay quiet are the ones with a gap to be quiet about.

If the window is one you open, or it has a crank, a handle or an inward sash, mount outside and stop measuring the depth. Depth was never the deciding input there.

If the frame is handsome and the room is a hallway or an office and not a bedroom, mount inside and accept the strip down each jamb. It is a real cost, and a small one when nobody is trying to sleep.

Where this figure comes from

Half Price Drapes · Crisp White French Linen Roman Shade

Listed from $179.20

What that covers: figure shown before the size calculation; the page carries a Price Calculator (Regular Price / Final Price) that recomputes on width x length. Sold per shade.

Build your size at Half Price Drapes

This is an affiliate link: a commission may come back to us, you pay nothing extra for it, and Half Price Drapes charges the same either way. The number above was read on 2026-09-19, so treat the live listing as the figure that counts. The image above comes from the Half Price Drapes listing, retrieved 2026-09-19.

If the recess is shallow and you still want the recessed look, the shutter at 1 3/4 inches fits where the other five do not, which is a strange thing to be true of the heaviest object on the page. The trade is that it has no plan B: no outside mount exists for it, and the window has to be square enough to take a rigid frame.

Where this figure comes from

Two Pages · TWOPAGES Veritas Hardwood Plantation Full Height Shutter

Listed from $107.99

What that covers: listed starting price (13 colourways, all at 107.99, no compare_at). Single or double panel, louver size and size entered in the configurator.

Build your size at Two Pages

This is an affiliate link: a commission may come back to us, you pay nothing extra for it, and Two Pages charges the same either way. The number above was read on 2026-09-19, so treat the live listing as the figure that counts. Photograph from the Two Pages catalogue, retrieved 2026-09-19.

Before any of that, get one thing out of the merchant, because it is the figure least likely to be on the page and the one that stops an outside mount dead. Ask it exactly like this: “On this listing, what is the minimum flat space the outside-mount brackets need, above the opening and at each side?” Then go and measure that, once, with the tape already in your hand.

Questions people ask

How much depth do you need for an inside mount? Between 1 3/4 and 3 5/8 inches across the six listings checked here. The figure belongs to the listing, never to the product family, so read the one you are buying.

Does an outside mount need any depth at all? No. These listings write that no minimum depth is required. What they ask for instead is a flat band of 1 to 2 inches for the brackets, and 2 to 4 inches of extra width.

Which mount blocks more light? The outside mount, and the brands say so themselves. Two of these listings point you outside to reduce the side gaps they publish on the inside mount.

Can you switch a shade from inside to outside mount after it arrives? On made-to-measure, no. The width was already calculated for the mount you chose. One merchant even lists the wrong mount among the faults it will remake.