How to Measure for Panel Track Blinds on Wide Windows

Key takeaways

• Measure in millimetres for accuracy, taking at least three measurements for width and drop and recording the smallest size for inside mounts.
• For outside mount panel track blinds, add an overlap of around 50–100 mm each side of the opening and 50–100 mm above and below, adjusting for skirting boards, coving and radiators.
• Decide your stack side early (left, right, split or centre) so the track and panels clear handles, vents and switches without blocking everyday use.
• If your window or door opening is not perfectly square, use the smallest measurement and consider increasing overlap or choosing an outside mount to hide uneven edges.
• For wide, heavy panel tracks, a motorised track system such as the Olide smart curtain motor track can keep operation smooth and reduce strain on the hardware.

Why accurate measurement matters for panel track blinds

Panel track blinds are especially popular for wide windows and doors because their large fabric panels glide smoothly along a track, covering large spans with fewer moving parts than traditional vertical blinds. However, those large panels also magnify any measuring mistakes. A gap of even 10 mm in the wrong place can let in a distracting shaft of light or leave part of a door frame exposed.

Unlike simple roller blinds that can sometimes be trimmed slightly after purchase, many panel track systems have fixed tracks, fixed carrier spacing and panels that are sewn with weighted hems. Once ordered, there is limited scope to adjust the width, so getting the measurements right up front is essential. A small investment of time now can save the cost and hassle of returns or replacements later.

Wide windows and doors add extra complexity. You may be spanning multiple panes, patio door leafs or a mix of fixed and opening sections. Handles often protrude into the space, and there may be skirting boards, coving or radiators to work around. This guide focuses on those wide, real-world openings and gives you a simple, repeatable process that you can use across your home.

Tools and preparation

Before you start measuring, gather the right tools and do some quick checks around the opening. This will make the actual measuring go faster and more accurately.

Tools you will need

• A good quality metal tape measure (at least 5 m long for wide spans)
• A pencil and notepad, or a notes app on your phone
• A small spirit level (helpful but optional)
• A step stool or stepladder for tall openings
• A helper for very wide doors or when measuring at height

It is best to measure in millimetres. Millimetres reduce rounding errors and match how most blind suppliers and DIY panel systems specify sizes. If your tape only shows centimetres clearly, you can still use it, but convert to millimetres (for example, 245.4 cm becomes 2454 mm) and always round as directed by your chosen supplier (usually down for inside mount, to be safe).

Check the space around your window or door

Spend a minute looking for anything that might interfere with the track or panels:

• Window and door handles (how far do they stick out?)
• Radiators or towel rails near the bottom
• Skirting boards, dado rails or picture rails
• Coving or deep ceiling mouldings above
• Light switches, sockets, vents or alarm sensors that could be covered
• Furniture that sits close to the opening

Decide whether you want an inside mount (fitted inside the recess) or an outside mount (track fixed to the wall or ceiling, covering the recess). For most patio and sliding doors, an outside mount is more practical, because it keeps the panels away from handles and allows generous overlap.

Tip: Take a quick photo of the window or door and mark up your planned measurements and overlaps. It is much easier to visualise stack side and overlap on a sketch or photo than in your head.

Inside vs outside mount: which is better for wide windows?

Panel track blinds can usually be installed either inside the recess or outside on the wall or ceiling. Each approach has pros and cons, and your measurements will differ depending on which you choose.

Inside mount (recess fit)

With an inside mount, the track is fixed to the top of the recess, and the panels sit within the opening. This gives a neat, built-in look and can work well for wide fixed windows with no protruding handles.

However, inside mounts are less forgiving on imperfect openings. If your recess is badly out of square, you may see small gaps where the panels meet the frame. Inside mounts are also tricky where door handles, trickle vents or hinges project into the recess, because the panels may catch as they slide.

Outside mount (face or ceiling fit)

With an outside mount, the track is fixed to the wall above the opening or to the ceiling, and the panels overlap the recess on all sides. This is usually the best choice for patio doors, sliding glass doors and large windows that you use frequently.

Outside mounts hide a multitude of sins: out-of-square openings, slightly uneven tiles, or frames with multiple joins. You can add generous overlap to reduce light gaps, and you can set the track far enough forward to clear handles and radiators. The rest of this guide will show you how to measure both types, but if you are unsure, an outside mount is normally the safer, more flexible option on wide spans.

How to measure width and drop for an inside mount

If you decide an inside mount is suitable, follow this method to measure accurately. Remember that for an inside mount, you are usually providing the actual recess size; the manufacturer will make the necessary deductions.

Step 1: Measure the recess width

Measure the width of the opening in three places:

• At the top of the recess (where the track will sit)
• In the middle
• At the bottom, just above the sill or floor

Record all three measurements in millimetres, then use the smallest as your recess width. This accounts for openings that taper or are slightly bowed. For example:

• Top: 2410 mm
• Middle: 2404 mm
• Bottom: 2400 mm

You would use 2400 mm as your recess width. Your supplier may then deduct a small amount (for example, 5–10 mm) to ensure the track fits comfortably. Always check whether you should enter the recess size or the blind size on their order form.

Step 2: Measure the recess drop

Next, measure the height (drop) of the recess in three places:

• Left side
• Centre
• Right side

Again, record all three in millimetres and use the smallest as your recess drop. For example:

• Left: 2268 mm
• Centre: 2273 mm
• Right: 2265 mm

You would order based on 2265 mm. If you have a window sill, measure to the top of the sill. If the blind will run down to the floor, measure to the finished floor surface (not underlay or floorboards).

Step 3: Check clearance and obstructions

Check that there is enough depth inside the recess to accommodate both the track and the stacked panels. Deep handles, trickle vents or inward-opening windows can interfere with the fabric panels as they slide.

If clearance is tight, you might need a shallow track, a ceiling mount set slightly forward, or an outside mount instead. Adjustable systems such as the GoDear Design adjustable panel track blind can give you a bit more flexibility in some situations, as the track can be positioned precisely where it clears handles and vents.

How to measure width and drop for an outside mount

Outside mounts are common for wide windows and sliding doors because they give better coverage and more generous clearances. Measuring is slightly different: instead of reporting the recess size, you are working out your desired blind size, including overlap.

Step 1: Decide on side overlap

For outside mounts, you usually want the panels to extend beyond the window or door frame on each side. This reduces light bleed and helps hide any out-of-square edges. A typical side overlap is:

• 50–100 mm each side for most windows
• 100–150 mm each side for large patio or sliding doors, or where you want deeper darkness

Formula for overall blind width:

Blind width = recess width + left overlap + right overlap

Example: A sliding door opening is 2400 mm wide. You choose 100 mm overlap each side:

• Left overlap: 100 mm
• Right overlap: 100 mm
• Blind width = 2400 + 100 + 100 = 2600 mm

This 2600 mm width ensures the panels cover the frame and give a tidy look even if the wall lines are not perfectly straight.

Step 2: Decide on top and bottom overlap

Next, decide how far above and below the opening you want the blind to extend. Consider coving at the top, skirting boards at the bottom, and any radiators or furniture.

• Above the frame: 50–100 mm is typical; more if you want to hide a curtain pole or transom.
• Below the sill or frame: If there is a sill, 50 mm below it usually looks good. If the blind goes to the floor, aim for 10–20 mm clearance above the floor to avoid dragging.

Formula for overall blind drop:

Blind drop = recess height + top overlap + bottom overlap

Example: A patio door opening is 2100 mm high. You mount the track 80 mm above the frame and want the panels to finish 10 mm above the floor, which is 50 mm below the frame bottom:

• Top overlap: 80 mm
• Bottom overlap: 50 mm
• Blind drop = 2100 + 80 + 50 = 2230 mm

Always measure from the actual track fixing point down to the desired bottom of the panels in at least two places (left and right). If you are mounting to the ceiling, measure from ceiling to floor and adjust for the clearance you want above the floor.

Step 3: Accounting for skirting boards and coving

Skirting boards and coving can affect how far from the wall your track needs to sit. Deep coving may mean moving the track slightly forward from the wall or fixing it to the ceiling. Skirting boards can push furniture forward, which may in turn affect how the panels stack and hang.

Check:

• The projection of your coving from the wall where the track will go.
• The thickness of skirting boards compared to the wall above.
• Whether any radiators overlap the window width, and how far they project.

In some situations, using a ceiling-mounted track or a track with adjustable brackets, like on many extendable panel blind kits, can help you project the panels just far enough forward to clear obstructions while still hugging the wall closely.

Choosing the stack side (left, right, split or centre)

Panel track blinds can usually be configured in several stacking options:

• Left stack: all panels stack to the left when open.
• Right stack: all panels stack to the right.
• Split stack: panels stack at both ends, opening from the centre like curtains.
• Centre stack: panels stack in the middle (less common, but available on some systems).

For wide windows and doors, the choice of stack can make everyday use much easier. Think about:

• Which side the main door leaf is on (you normally want the panels to stack on the wall side opposite the main access).
• Where furniture is placed; avoid stacking behind tall units or bookcases.
• Handles or vents that might catch the panels if they stack in front of them.
• Where you usually stand to open and close the blinds.

For example, if your sliding door opens from left to right and the fixed pane is on the right, a right-hand stack works well: the panels stack over the fixed pane, leaving the door leaf clear. If you have a main door in the middle of a wide set of bi-folds, a split stack may give equal access from both sides.

Tip: If you are planning a motorised track, such as a smart curtain motor system, decide the stack side before ordering; some motor units are handed, and the drive sits at one end of the track.

Handling door handles, radiators and other obstructions

Wide doors and windows often come with chunky handles, mullions and nearby radiators that can interfere with panel operation. The key is to plan for these when deciding your track position and overlap.

Door and window handles

Measure how far the handle protrudes from the face of the frame. Then ensure that the track is mounted far enough forward so that the back of the panels clears that projection by at least 10–15 mm.

For example, if your handle projects 60 mm from the frame, look for a track and bracket combination that lets the panel sit at least 75 mm from the frame. If this is not possible with a wall mount, consider a ceiling mount slightly forward of the frame. Some extendable track systems and adjustable panel kits, similar to the GoDear adjustable sliding blind, are particularly useful in these situations because you can fine-tune the mounting position.

Radiators, skirting and nearby furniture

Radiators under windows can limit how low you can safely drop the panels without them sitting directly on a hot surface. In most cases, you will want the panels to stop 30–50 mm above the top of the radiator.

Measure from your proposed track position down to the top of the radiator, then subtract 30–50 mm. This gives you your maximum practical drop. If this is lower than you initially planned, adjust your top overlap to keep the bottom line of the panels where you want it visually.

For furniture, ensure that when the panels are stacked, they are not pressed hard against tall cabinets or shelves. This can cause creasing and make operation stiff. You might need to reduce your side overlap slightly on the furniture side and increase it on the opposite side to keep the overall width suitable.

What to do if your window or door is out of square

Many wide openings are not perfectly square. Walls may bow, frames may lean slightly, and floors can slope. The multi-point measuring method already helps you pick up on this, but you may need to adjust your plan accordingly.

How to spot an out-of-square opening

Signs that your opening is out of square include:

• Top, middle and bottom width measurements differ by more than 10–15 mm.
• Left, centre and right drop measurements differ noticeably.
• A spirit level shows that the sill or head is not level.

If the variation is small (a few millimetres), an inside mount may still work fine, especially if you accept tiny light slivers in the worst spots. If the variation is larger, an outside mount with generous overlap is more forgiving and often looks cleaner.

Choosing the right approach

For inside mounts on out-of-square openings, it is usually safest to work with the smallest width and smallest drop. This ensures the track and panels fit everywhere, though you may see slightly larger gaps in the wider or taller parts of the opening.

For outside mounts, you have more creative freedom. You can level the track with a spirit level, then use generous overlaps to hide uneven edges. Because the panels hang from the track, they will appear straight and level, even if the frame beneath is not. This is one of the reasons outside mounts are so popular for older properties and large doorways.

Worked examples and quick sizing formulas

To make these steps easier to apply, here are two quick worked examples you can adapt to your own measurements.

Example 1: Wide sliding patio door (outside mount)

You have a sliding patio door that measures 3000 mm wide and 2100 mm high. You want an outside-mounted panel track blind.

1. Decide overlaps: 125 mm each side, 80 mm above, 20 mm below the frame.
2. Width calculation: 3000 + 125 + 125 = 3250 mm blind width.
3. Drop calculation: 2100 + 80 + 20 = 2200 mm blind drop.
4. Check clearances: Door handle projects 55 mm. You choose a track and bracket setup that positions the back of the panel 75 mm from the frame, giving safe clearance.
5. Choose stack side: Main opening leaf is on the left, fixed pane on the right, so you opt for a right-hand stack.

Example 2: Extra-wide fixed window (inside mount)

You have a fixed picture window in a recess, used only for light, not as a door. You decide on an inside mount.

1. Measure width: Top 2590 mm, middle 2586 mm, bottom 2588 mm; use 2586 mm as recess width.
2. Measure drop: Left 1405 mm, centre 1403 mm, right 1407 mm; use 1403 mm as recess drop.
3. Check depth: Recess depth is 85 mm, handles project only 20 mm; plenty of room for a track and panels.
4. Order details: If the supplier asks for recess size, you provide 2586 mm width x 1403 mm drop in millimetres, and they make the small fitting deductions.

Using adjustable and motorised panel track systems

If you are not confident about exact final widths, or if you might move the blinds to another opening in future, adjustable panel track systems can be useful. Products like an extendable panel track blind kit offer telescopic tracks that cover a range of widths, with panels that can be trimmed to your exact drop.

For especially wide or heavy setups, or where you will open and close the blinds often, think about a motorised track system. A compact motorised track, similar in concept to the Olide DIY Wi‑Fi smart curtain motor track, can make operation almost effortless. Your measurements for motorised tracks are usually the same as for manual tracks, but double-check the manufacturer’s minimum and maximum track lengths before finalising your width.

Troubleshooting common measuring problems

Even with a careful plan, a few issues crop up frequently when measuring for panel track blinds on wide windows and doors.

• Problem: Track length options do not match your ideal width.
  
  Solution: Look for extendable or cut-to-size tracks within a range that comfortably covers your required width. If you must choose between slightly wider or slightly narrower, wider is usually better for outside mounts, as the extra overlap helps light control.
• Problem: Low ceiling above a tall door leaves little room for a top overlap.
  Solution: Use a ceiling-mounted track that runs as close to the ceiling as possible, and accept a smaller top overlap (for example, 30–40 mm). Increase side overlap slightly to help with light control.
• Problem: You have multiple doors in a row with varying heights.
  Solution: Base your measurements on the tallest door and mount the track level. The panels will hang evenly, and the overlap above shorter doors will simply be slightly larger, which is usually not noticeable.
• Problem: Unsure whether to order in centimetres or millimetres.
  Solution: Always measure in millimetres and check the order form carefully. Many systems accept millimetres directly. If the supplier uses centimetres, divide your millimetre measurement by 10 and round according to their guidance.

Conclusion

Measuring for panel track blinds on wide windows and doors is all about method. With a metal tape measure, a notepad and a few simple formulas, you can work out accurate sizes that give you generous coverage, smooth operation and a clean, tailored look. Focus on millimetre accuracy, measure in several places, and always plan for overlaps and obstructions rather than trying to adapt your blinds after they arrive.

If you prefer a flexible solution, an adjustable panel track blind can take some of the pressure off precise width measurements, while a motorised track setup such as a compact Wi‑Fi curtain motor can make wide spans effortless to control. Whichever system you choose, a careful measuring session now will pay off every time you slide those panels open and closed.