How to Measure for Venetian Blinds

Whether you’re dressing up a cosy kitchen window or adding a sleek finish to your living room, measuring correctly ensures your new blinds not only look the part but work flawlessly too. A precise measurement means:

• A perfect fit that looks tailor-made
• Maximum light control to suit your needs
• Reliable privacy where and when you need it
• A polished, professional finish that elevates your space
• Avoiding costly mistakes or returns

In this guide, we’ll walk you through the two main fitting options: recess fitting (inside the window frame) and exact fitting (outside the window recess). We’ll also share general measuring tips to help you avoid common pitfalls and get the most accurate results.

Don’t worry, it’s simpler than you think! Follow our step-by-step guide, and you’ll be a measuring pro in no time.

Essential Tools You’ll Need

Before you get started, gather the right tools to ensure your measurements are spot-on. Here’s what you’ll need:

Steel Tape Measure

Always use a steel tape measure, not a fabric one. Steel is rigid and accurate, while fabric tapes can stretch or sag, leading to incorrect readings. Make sure your tape is long enough to reach the widest and tallest parts of your window with ease.

Pencil

A simple pencil is ideal for marking reference points and jotting down quick notes. It’s easy to correct if you need to make adjustments.

Paper or Notebook

Have a piece of paper or notebook handy to write down each measurement immediately. It’s surprisingly easy to forget or misremember a figure, even seconds later!

Step Ladder (if needed)

If you’re measuring a tall or hard-to-reach window, use a sturdy step ladder. Prioritise safety—don’t overstretch or balance on unstable furniture.

Calculator (optional but helpful)

While not essential, a calculator can be useful for double-checking figures or converting units if needed, helping to avoid minor errors that could make a big difference.

Before You Start: Key Considerations & Pro Tips

Before you reach for the tape measure, there are a few crucial things to keep in mind. Getting these right at the start can save you time, money, and potential frustration later on.

Measure Twice, Order Once

This is the golden rule of measuring for blinds. Always double-check every measurement—once may be a fluke, twice confirms it’s right. Re-measuring helps catch errors before they turn into misfitting blinds.

Which Way Round?

At DotcomBlinds, all measurements must be provided in the order of:

👉 Width first, then Drop (height).

Getting these the wrong way round is one of the most common (and avoidable) order errors, so always double-check the sequence before submitting.

Identify Obstructions

Take a moment to scan the window area for anything that could interfere with the blind’s movement or positioning. Key things to look out for include:

• Window Handles: Do they stick out? Make sure there’s enough clearance so the slats or headrail aren’t obstructed.
• Tiles or Dado Rails: Common in kitchens and bathrooms—these may narrow the usable space inside the recess.
• Vents or Airbricks: If you’re fitting outside the recess, make sure the blind won’t block essential ventilation.
• Furniture or Radiators: These might sit below or beside the window. For outside recess fitting, make sure the blind can hang freely without obstruction.

Determine Your Fitting Type

Perhaps the most important decision you’ll make. There are two standard fitting styles:

Inside Recess Fit

The blind fits neatly within the window frame itself, giving a flush, built-in look. Ideal if you want a clean finish and still plan to use curtains or want to show off decorative window features.

Exact / Outside Recess Fit

The blind is mounted outside the window recess, overlapping the opening. This style is best for:

• Covering less-than-square recesses
• Improving blackout performance
• Avoiding obstructions inside the recess
• Making small windows appear larger

Measuring for an “Inside Recess” Fit (Fitting Inside the Window Frame)

An inside recess fit means your Venetian blind will sit snugly within the window reveal, offering a clean, streamlined look. This is a popular choice for modern interiors, especially when you want the blind to feel built-in or when pairing with curtains.

What DotcomBlinds Does

Good news — you don’t need to make any deductions yourself.
When you select an inside recess fit, DotcomBlinds will automatically make the necessary deductions to ensure your blind fits perfectly and operates smoothly within the space.

“We’ll take care of the necessary deductions so your blind fits perfectly without snagging.”

Let’s walk through how to measure accurately.

How to Measure the Width (Inside Recess)

1. Measure the full width of the window recess in three places:

• Top
• Middle
• Bottom

1. Important: Write down the narrowest of the three measurements.
   This ensures your blind won’t catch or get stuck if the walls aren’t perfectly straight.

2. Record your measurement in millimetres (mm) and label it clearly as the width.

How to Measure the Drop (Inside Recess)

1. Measure the full height (drop) of the recess in three places:

• Left
• Centre
• Right

1. Important: Use the shortest measurement.
   This avoids the blind dragging on the sill if your window frame or sill is slightly uneven or sloped.

2. Again, record it in millimetres (mm) and label it as the drop.

🔔 Important Note:

Do not make any deductions yourself.
We’ll handle that part for you.

Seriously — don’t adjust anything for clearance or tolerance.

Repeating for emphasis: Do not make any deductions. Simply supply the exact recess measurements and let DotcomBlinds do the rest.

Recess-Specific Obstructions to Watch Out For

When fitting inside a recess, certain obstructions can affect how your blind fits or operates:

• Protruding Window Handles:
  If handles stick out significantly, they may interfere with the slats or headrail. In such cases, the blind may need to be face-fixed into the top of the recess (lintel) rather than mounted deeper within the reveal.
  → Tip: If your handles are deep or unusually shaped, it’s best to contact DotcomBlinds for tailored advice.
• Sloping Sills:
  It’s not uncommon for window sills to slope slightly.
  → This is why measuring the shortest drop is so important, as it prevents the bottom of the blind from dragging or bunching.

Measuring for an “Exact” / “Outside Recess” Fit (Fitting Outside the Window Frame)

An exact fit means the blind will be mounted outside the window recess, overlapping the window opening itself. This style is ideal for maximum light control, flexibility with obstructions, and achieving a bold visual impact.

What DotcomBlinds Does

When you choose an exact fit, DotcomBlinds will manufacture your Venetian blind to the precise measurements you provide, without making any deductions or additions.

“We will make your blind to the exact measurements you give us, with no deductions.”

So it’s important to measure exactly how much coverage you want.

Why Choose an Exact / Outside Recess Fit?

• ✅ Improved light blocking, especially around the edges

• ✅ Makes small windows appear larger

• ✅ Perfect for awkward recesses, such as those with:

• Protruding window handles
• Deep window sills
• Sloping or uneven recess walls

How to Measure the Width (Exact Fit)

1. Decide how much you want the blind to overlap the window on each side.

   • We recommend at least 50mm (5cm) on both the left and right for effective light coverage.

2. Measure the width of the window opening.

3. Add 100mm total (50mm each side) to your measurement.

   • This gives the blind enough coverage to block light effectively and provide a neat appearance.

4. Measure the total area you want the blind to cover, from edge to edge.

   • This is your final width measurement.

5. Think about where you’ll mount the blind:

   • Wall-mounted: Above and wider than the window frame.

   • Ceiling-mounted: Attached to the ceiling or a soffit, with a vertical drop past the window.

How to Measure the Drop (Exact Fit)

1. Decide how much you want the blind to overlap at the top and bottom of the window.

   • We recommend a minimum of 50mm (5cm) above the window to hide the headrail and block more light.

   • For the bottom, consider whether you want the blind to:

     • Stop just above the sill

     • Rest lightly on it

     • Overlap slightly

     • Hang freely (e.g., if extending to the floor)

2. Measure from your chosen top point to your desired bottom point.

   • If you’re going floor to ceiling, measure to 10mm short of the floor to avoid dragging.

3. Make sure to consider any radiators, furniture, or vents beneath the window when choosing your bottom position.

🔔 Important Note:

These are the finished blind dimensions, so measure carefully!
DotcomBlinds will make your blind exactly to the width and drop you submit. No adjustments will be made.

Specific Considerations for Venetian Blinds

While measuring is the most critical step, there are a few Venetian-blind-specific details worth factoring into your planning. These considerations can help you make smarter choices and avoid surprises once your blind is installed.

Stack Height

When a Venetian blind is fully raised, the slats don’t disappear — they gather into a “stack” at the top of the window. This stack will partially obscure your view or daylight, particularly for taller windows.

What Affects Stack Height?

• Slat width
• Blind drop (height)
• Material (wood, faux wood, aluminium)

Here are some approximate stack heights for standard slat sizes, based on an average blind with a 1500mm drop:

For example, a 1500mm drop Venetian blind with 50mm slats may have a stack height of approximately 150–200mm when fully raised.

These figures are general guidelines — for precise measurements, we recommend contacting DotcomBlinds directly, especially if stack height is a concern for your specific installation.

Why This Matters:

• If you want the blind to clear the window entirely when raised (especially for exact/outside recess fitting), you may need to install it higher above the window to accommodate the stack.
• For inside recess fitting, the stack will reduce how much of the window is visible when the blind is open.

Slat Width Choice

While not a direct measuring factor, your choice of slat width does impact:

• Overall appearance:

• 25mm: Slim and contemporary
• 35mm: A balance between minimal and bold
• 50mm: Classic and chunky — ideal for larger windows

• Stack height:

• Narrower slats create a taller stack
• Wider slats form a shorter stack relative to the same blind drop

If preserving as much of your view as possible is a priority, wider slats may be a better choice.

Control Side

Before placing your order, don’t forget to choose which side you want the controls on:

• Tilt Control (wand or cord): For adjusting the angle of the slats
• Raise/Lower Cord: For lifting the blind up or down

This is usually selected during the checkout or customisation stage.
Think about what’s most practical for your window location — for example, you may want the controls on the opposite side of a window handle, or on the side closest to your dominant hand.

Ready to Order?

Ready to find your perfect Venetian blinds?
Start browsing our full range of made-to-measure options here:
👉 Browse our Venetian Blinds

Need a sample first?
Order your free samples to see the colours, textures, and finishes up close before you buy:
👉 Get Your Free Samples

If you have any questions about measuring, fitting, or choosing the right blind, our expert team is just a message or phone call away. We’re here to help you get it right, first time.