How to Measure for Custom Roller Shades

Quick Answer: For an inside mount, check the frame depth first, measure the width at three heights and use the smallest reading, measure the height at three points and use the largest, and round both down to the nearest 1/8 inch^[5]. For an outside mount, add 3 to 6 inches to the width and height for full coverage^[5]. Weffort’s custom cordless roller shades start at $99.99 and are built to those numbers rather than trimmed to fit^[1].

One-line rule: Smallest width, largest height, round down to 1/8 inch.

Those three rules are Weffort’s published measuring instructions, and they answer the questions that cause most reorders. This guide walks through how to measure for a roller shade at a real window, including the depth minimums that decide between inside mount roller shades and an outside mount, and the one specification that explains why a correctly measured blackout shade can still show light at the edges.

The Numbers You Need Before You Order

Everything below comes from Weffort’s official measuring guidance^[5]. Have these measurements ready before you start the order form.

Specification	Inside mount	Outside mount
Minimum frame depth	1 3/4 inches (4.5 cm) for a cassette valance; 2 inches (5 cm) for a square valance	Not applicable; needs 2 to 3 inches of flat space above the window for brackets
Width rule	Measure at top, middle, and bottom; use the smallest, rounded down to the nearest 1/8 inch	Add 3 to 6 inches (7.6 to 15.2 cm) to the exact window width
Height rule	Measure at left, center, and right; use the largest, rounded down to the nearest 1/8 inch	Add 3 to 6 inches to the window height
Fabric width	Roughly 1 3/16 inches (about 3 cm) narrower than the valance, meaning the ordered width	Same, but the added overlap absorbs it

That last row is the one most people have never seen, and it explains more than any other number here. It is also why the depth check comes first: if your recess is shallower than the minimum for the valance you want, no amount of careful measuring will make an inside mount work.

Pick Your Mount Type First

Before you touch the tape measure, decide what kind of fit you want. The mount choice changes which dimensions you record and how much overlap you plan for.

Window condition	Recommended mount	What to record	Why it matters
Recess at least 1 3/4 inches deep, reasonably square	Inside mount	Smallest width, largest height, rounded down to 1/8 inch	Gives the cleaner built-in look, and the depth clears a cassette valance[5]
Bedroom or media room where blackout matters most	Inside mount, plus light blockers	Smallest width, largest height, rounded down to 1/8 inch	Inside mount with light blockers is the strongest setup against edge light[1]
Recess under the minimum depth, or handles, cranks, or trim in the way	Outside mount	Coverage area plus 3 to 6 inches on width and height	Avoids hardware conflicts and gives the fabric a clean travel path[5]
Frame that is visibly out of square	Outside mount	Coverage area, not the recess	A square shade in front of a wonky opening reads better than one fitted inside it

If the opening is only slightly uneven and deep enough, an inside mount still looks tailored, because the shade is built to your actual readings rather than a nominal size.

Before You Start: Tools, Conditions, and Fabric

The method that follows is built on Weffort’s official measuring guidance for its custom roller shades^[5], so the readings you take here are the readings its order form expects. Because every shade is made to order rather than cut down from a stock size, the numbers you submit are the numbers the shade gets built to, which is what makes a short prep step worth the few extra minutes.

That prep is simple. Use a steel tape with clear 1/8-inch markings, a pencil, and a notepad or your phone to record each reading. If the top of the opening is high, bring a stable ladder so you can measure straight across instead of guessing from an angle.

Decide the fabric before final measuring, because room goals shape how you plan the fit. Blackout is usually right for bedrooms and media rooms. Light-filtering works better in living spaces where you want privacy without closing the room in. PVC-free sunscreen is the practical option when glare control matters but you still want outward visibility. Samples are 5 x 8 inches, with blackout and light-filtering swatches at $6.99 each or $11.98 combined, plus a 30-day discount lock after ordering^[1].

Accessories matter too. Light blockers help with edge light, and power choices for solar or USB setups can affect where you want the shade mounted. Motorized shade technology has shifted heavily toward battery power with solar charging, which makes planning for power part of the fit conversation rather than an afterthought^[2].

Finally, check for obstructions before you measure: handles, cranks, trim depth, sill projection, and whether the frame is square enough for an inside mount. If the tape rocks, catches, or will not sit flat inside the recess, that is already telling you something about the window.

Step 1: Inside Mount vs Outside Mount Roller Shades

Choose inside mount whenever the recess is deep enough and reasonably square; treat outside mount as the fallback for windows that cannot take one.

Start with the depth, because it settles the question before preference does. Measure from the front edge of the frame to the glass: an inside mount needs at least 1 3/4 inches (4.5 cm) for a cassette valance, or 2 inches (5 cm) for a square valance^[5]. Come up short and the choice is made for you. If you are ordering a battery-powered motorized shade, leave yourself a little more room than the minimum so you can reach the charging port later without dismounting the headrail.

With the depth confirmed, the two paths diverge. An inside mount means measuring the opening the shade must fit inside. An outside mount roller shade means measuring the area you want covered, then adding 3 to 6 inches (7.6 to 15.2 cm) to both width and height, and confirming 2 to 3 inches of flat space above the window for the brackets^[5]. Shallow frames and French doors usually land here, since neither leaves enough recess for a valance.

Worth knowing before you decide: if darkness is the priority, the strongest setup is an inside mount paired with light blockers, not an outside mount. Sitting inside the recess keeps the fabric close to the glass and contained by the frame, and the light blockers then close off the edges that the recess alone leaves open. An inside mount on its own comes next. Outside mount is what you fall back to when the window cannot take an inside mount, and the 3 to 6 inches of overlap is the compensation for that.

This is where custom sizing earns its keep. Off-the-shelf blinds ask you to pick the nearest width and live with the compromise. A custom shade is ordered to the real dimensions of your window, so you are not trimming a finished product at home or accepting obvious gaps because the store only stocked widths in two-inch jumps.

Tip: order samples before you submit final dimensions if you are still deciding on color or fabric behavior. Swatches are 5 x 8 inches, and the lineup includes 35 blackout colors and 38 light-filtering colors^[1]. Spending $6.99 to confirm the look is cheaper than second-guessing a full custom order later.

Step 2: Measure Width in Three Places

Place the tape inside the frame, measure left-to-right at the top, middle, and bottom, keep it level, and record all three. For an inside mount, use the smallest of the three and round it down to the nearest 1/8 inch^[5].

This is the step that separates a made-to-measure result from a “close enough” one. Older homes, repainted frames, and slightly bowed jambs often produce three different width readings even when the window looks straight from across the room. A custom shade can only fit as well as the numbers you give it.

A realistic example: 35 7/8 inches at the top, 35 13/16 at the bottom, and 35 3/4 in the middle. The middle reading is the smallest, so that is your width, and it is already on a 1/8-inch mark. Had it read 35 25/32, you would round down to 35 3/4 rather than up. The narrowest point governs because it is the tightest spot the hardware has to clear. For an outside mount, ignore this entirely and work from the coverage you want instead.

You will know the frame is uneven when the spread between the three readings is noticeable rather than nearly identical. That does not make the window a problem. It means the window behaves like many real windows do, which is exactly why measuring three points matters. Keep the tape level, pull it straight from edge to edge, and write each number down immediately. A note format like width-top, width-middle, width-bottom prevents mix-ups later.

Step 3: Measure Height in Three Places and Check Clearance

Measure top-to-bottom at the left, center, and right inside the frame, keeping the tape vertical, and record all three. For an inside mount, use the largest of the three and round it down to the nearest 1/8 inch^[5].

This is where the height rule surprises people, because it runs opposite to the width rule. Width takes the smallest reading, height takes the largest. That is the instruction as published, and the useful thing is simply to apply it rather than reason your way to it, because getting the two backwards is what produces a misfit.

For a recessed window, take the three vertical readings from the top inside edge down to the sill or the point you want the shade to reach. Then run a quick obstruction check for a projecting sill, decorative trim, window handles, tilt latches, or cranks that could sit in the fabric’s path^[3]. A short recessed-window checklist:

• Frame depth
• Sill projection
• Handle or crank clearance
• Any trim that narrows the opening
• Whether the fabric can travel without rubbing hardware

Motorized roller shades need a clean travel path. Once the brackets are installed, the shades snap into place and are ready to operate, which is exactly why clearance matters^[3]. Installation can be straightforward, but only if the opening gives the hardware and fabric room to move cleanly. If the shade would hit a handle or crank during travel, that is a mount-planning issue, not something to ignore and hope away.

Step 4: Handle Uneven or Irregular Windows Without Guessing

Treat an uneven window as a measuring job, not a guessing game.

Custom manufacturing handles a real opening far better than a fixed-size blind, but only if you apply the rules consistently instead of improvising. Never average your three readings. Width takes the smallest, height takes the largest, both rounded down to the nearest 1/8 inch^[5]. A bowed jamb is a good example: the point where it bulges inward is the number that counts, not the wider sections either side of it.

One thing worth knowing when the readings spread widely: if the width varies by roughly half an inch or more, an inside-mount roller shade will look visibly off inside the opening, and an outside mount is the cleaner answer. That is a squareness problem, not a light problem.

If the frame is only slightly out of square, an inside mount can still look tailored, because the shade is built for the real opening rather than a nominal size. If the frame is visibly irregular or too shallow for a valance, an outside mount gives more control because you are no longer trying to fit the shade inside a flawed recess. The takeaway is specific: custom sizing reduces compromise, but it does not erase the geometry of the window. It works best when you measure what is actually there.

Step 5: Plan for Light Gaps and Blackout Performance

Measure tightly for fit, then plan accessories separately if edge light matters. For a dark room the ranking is inside mount with light blockers first, inside mount alone next, outside mount last.

Here is the specification that explains it, and it is published rather than a rule of thumb: the fabric is roughly 1 3/16 inches (about 3 cm) narrower than the valance, which is the width you order^[5]. So on a 36-inch inside-mount order, the fabric itself is closer to 34 3/4 inches, and that difference is split between the two sides. The fabric has to be narrower to travel freely inside the hardware, which means a blackout shade measured perfectly will still admit a line of light at each edge in a dark room.

Once you know the number, the order of solutions follows from it, strongest first:

1. Inside mount plus light blockers. This is the best setup for darkness. The shade sits inside the recess with the fabric close to the glass, and the light blocker addresses the edge directly: a track along each side that wraps the fabric edge so the shade still slides freely while blocking light past it, which is what removes the halo effect on shades sold as blackout^[1][3].
2. Inside mount on its own. Still strong. The recess itself contains most of the light path, and a well-measured blackout fabric is often dark enough to sleep in without accessories.
3. Outside mount. The fallback when the window cannot take an inside mount. The 3 to 6 inches of added width puts the fabric past the opening so the edge gap lands over wall rather than glass^[5], which compensates for losing the recess but does not beat it.

That order matters because the instinct is usually backwards. Adding overlap in front of the window sounds like the stronger fix, but the shade is then hanging off the wall with the fabric further from the glass. Reach for outside mount when the depth, the hardware, or a crooked frame rules out an inside mount, not as your first move on a dark bedroom.

The mental model for measuring stays simple: precise dimensions improve the fit, accessories improve the edge. They are related but not the same thing, so decide the mount from the window and the light blocker from the room.

Step 6: Match Measurements to the Right Shade and Room

Use the same measuring method for every fabric, then choose the mount and overlap strategy based on how the room is used. All three fabrics start at $99.99^[1].

• Bedrooms and media rooms: blackout is the natural fit, and this is where an inside mount plus light blockers deserves the most attention if edge light is a concern.
• Living rooms and dining areas: light-filtering usually matches best when you want privacy without shutting out daylight; the pressure to maximize edge coverage is lower than in a blackout room.
• Offices, kitchens, and glare-prone rooms: PVC-free sunscreen is the practical option when you still want outward visibility, and mount choice is driven more by hardware clearance and finish than by total darkness.

Samples make this easier before you lock in dimensions. Swatches are 5 x 8 inches, with 35 blackout colors and 38 light-filtering colors^[1]. Once the room goal is clear, the method is the same everywhere: same tape, same 1/8-inch precision, different decisions about overlap and accessories.

Why Custom Precision Is Worth the Effort

The biggest advantage here is not hype. It is that affordable custom sizing lets you avoid DIY cutting and the side-gap compromises of fixed-width blinds. It helps to think in tiers rather than logos.

Tier	Entry-price framing	Custom sizing	Sample program	What it means for your window
Fixed-width retail blinds	Low sticker price	No; nearest stocked width	Rare	You choose the closest size and accept gaps or trim at home
Value custom motorized (including Weffort)	From $99.99	Yes	Yes ($6.99 swatches)	Built to your exact opening, with fabric samples to confirm first
Premium dealer and design brands	Several hundred dollars and up	Yes	Varies	Very large fabric libraries and dealer service, at a much higher entry price

That spread is what makes careful measuring worth the effort. At a $99.99 starting point, the custom route stays accessible for DIY-minded buyers who want a made-for-the-window result without premium-brand pricing, while premium tiers climb into the hundreds for comparable roller shades^[1]. Either way, the measurement discipline is identical; only the price of a mistake changes.

Confidence Signals: Motor, Packaging, and Buyer Impressions

Accurate measurement feels more worthwhile when the product itself is built with care. Hands-on testing describes the shades as affordable motorized shades with Zigbee, Z-Wave, and Matter-over-Thread motors, available in custom dimensions on the official store and Amazon, which matters for a guide about precision: this is a made-to-order system, not a trim-it-yourself blind^[2]. The same review reported factory pre-calibration and simple installation, noted double-boxed packaging protected on all sides, and summarized that the blinds move slowly by default but are very quiet^[2].

Buyer sentiment supports it: the motorized blackout listing shows 4.8 out of 5 from 536 ratings on Amazon^[4]. Certification, warranty length, and lifespan vary by series, so check those on the product page for the shade you are ordering.

FAQ

How do you measure for roller shades?
Three steps. Check the frame depth first, since an inside mount needs at least 1 3/4 inches for a cassette valance or 2 inches for a square valance^[5]. Then measure the width at the top, middle, and bottom and take the smallest reading. Then measure the height at the left, center, and right and take the largest. Round both down to the nearest 1/8 inch and submit those numbers as measured. For an outside mount, skip the recess entirely and add 3 to 6 inches to the window’s width and height instead.

Should I round up or down to the nearest 1/8 inch?
Down. The published instruction is to round down to the nearest 1/8 inch (0.125 inch) for both the inside-mount width and height^[5]. Never round up to a whole inch because it looks tidier, and never round up “for margin” on the width, since that is the dimension that has to clear the tightest point of the opening.

Should I subtract anything from my measurements to be safe?
No. Submit the readings as measured, rounded down to the nearest 1/8 inch. The manufacturer applies its own allowance so the hardware fits the recess. If you deduct as well, both deductions stack and you end up with visible gaps at the sides.

What if the top and bottom widths are different?
Keep all three readings and submit the smallest for an inside mount, because that is the tightest point the hardware must pass^[5]. Varied readings are normal in older or repainted frames. Note that height works the other way: there you submit the largest of the three.

Will custom sizing completely remove blackout side gaps?
Not on its own. Custom sizing improves the fit, but the fabric still runs roughly 1 3/16 inches narrower than the ordered width so it can travel freely, which leaves a line of light at each edge^[5]. For a genuinely dark room, an inside mount with light blockers is the strongest combination, an inside mount alone is next, and an outside mount is the fallback when the window will not take one^[1][3].

Should I order samples before I take final measurements?
Yes, if you are still deciding between blackout, light-filtering, or PVC-free sunscreen. Samples are 5 x 8 inches and help you confirm color, texture, and room suitability before locking in a custom order^[1].

Is exact sizing safer than trimming motorized blinds at home?
Yes. The whole advantage of this category is that the shade is built to the window instead of being cut down after purchase, which is especially valuable with motorized cordless shades where preserving the factory-built structure beats improvising with tools at home.

Bottom Line

Weffort’s appeal here is straightforward: custom motorized roller shades from $99.99, in blackout, light-filtering, and PVC-free sunscreen, with sample-based buying support and accessories that refine fit and light control^[1]. Measure the actual opening in several places, record every number to 1/8 inch, and choose the mount type before ordering, and you get what custom shades are meant to deliver: a made-to-measure result without the compromises of fixed-width blinds or the gamble of DIY cutting.

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References

• 1. Weffort official website — custom sizing, blackout/light-filtering/PVC-free sunscreen fabrics, light blockers, sample program (5 x 8 inch swatches, 35 blackout and 38 light-filtering colors, 30-day discount lock), and pricing. ↩
• 2. Weffort Smart Shades with Thread review — SmartHomeScene — hands-on review noting custom dimensions, factory pre-calibration, simple installation, double-boxed packaging, quiet operation, and the shift toward battery power with solar charging. ↩
• 3. Motorized Blackout Roller Shades with Side Channels — explanation of edge light on roller shades and how side channels wrap the fabric edge to remove the halo effect. ↩
• 4. Amazon — WEFFORT Motorized Roller Shades, 100% Blackout — product listing showing 4.8/5 from 536 ratings. ↩
• 5. How to Measure Roller Shades — Weffort official measuring guide — inside-mount minimum depths of 1 3/4 inches for cassette valances and 2 inches for square valances; width measured at top, middle, and bottom using the smallest reading rounded down to the nearest 1/8 inch; height measured at left, center, and right using the largest reading rounded down to the nearest 1/8 inch; fabric width roughly 1 3/16 inches narrower than the ordered valance width; outside-mount guidance to add 3 to 6 inches to width and height and allow 2 to 3 inches of flat space above the window for brackets. ↩