How to Measure and Install the Right Blinds and Shades

Learning how to measure for blinds and shades helps avoid pricey mistakes. The correct dimension for blinds and shades ensure a proper fit. Getting accurate measurements is easy if you have the right tools and insights.

Tools and Materials


  • Tape measure
  • Level
  • Screwdriver
  • Drill
  • Pencil
  • Miter saw or hacksaw
  • Step stool


  • Blinds or shades
  • Mounting brackets
  • Screws and anchors
  • Paper and pencil
  • Hold-down brackets (optional)
  • Cleaning supplies

Inside Mount vs. Outside Mount Blinds and Shades

Inside Mount vs. Outside Mount Blinds and Shades

Both offer different methods of installing window blinds and shades. They vary in how the window treatments attach to the window frame or inside the window recess.

Inside Mount

Inside mount refers to fitting the blinds or shades within the window frame or recess. The window treatment’s headrail is attached to the window opening.

Inside mount creates a clean, streamlined look, giving the illusion of a built-in window treatment. It doesn’t cover any part of the window frame, which allows more natural light.

The mount type also doesn’t occupy much of the room’s interior space. It’s ideal for smaller rooms or windows close to furniture.

Outside Mount

Outside mount are window coverings mounted on the exterior of the window casing. Mounting them outside the window frame allows maximum light control.

They cover the entire window area to prevent light from seeping around the edges. They’re ideal for windows where blinds are the sole cover.

Outside mount window treatments don’t require any specific depth. They’re suitable for shallow windows or windows with obstructions like handles or cranks.

Measuring for Inside Mount Blinds and Shades

First, check if there’s enough room to install a blind and its header in the window opening. You must also ensure the window’s edge doesn’t flush with the wall.

Measuring for Inside Mount Blinds and Shades

Step 1: Measure Width

Width is the distance from one inside edge of the casing to the other. Use tape to measure the recess at three horizontal points.

Hold both ends of the tape on the inside edges of the recess at the top, middle, and bottom. Measure from one inside edge to another and not from the outer edges of the window trim frame.

Also, make sure to take the measurements to the nearest ⅛ inch. If the widths aren’t uniform, use the narrowest measurement. This ensures that the blinds are free to operate without obstruction. Use the top-most width to install vertical blinds, sheer, or roller shades.

Step 2: Measure the Height

Height or drop is the distance from the sill to the bottom edge of the upper casing. To measure the height for the blind, run your tape inside the window frame in three vertical points.

Hold the tape on the inside edges and measure the recess’s right, left, and middle sections. Ensure the measurements are within ⅛ inch.

Extra-long blinds aren’t troublesome, but blinds that are too short let in excess light. If the lengths differ, use the longest of the three height measurements for the blinds.

Step 3: Measure Depth

Depth focuses on the flat surface on the bottom side of the upper window casing. The flat surface lets you attach a headrail or housing for the blind’s mechanical components. Depth is crucial since you need specific depths to fit inside-mount blinds inside the window.

Measure the inside depth to the nearest ⅛ inch at the top of the window frame while considering window obstacles. The shortest measurement denotes the depth you’ll use for the blinds.

Measuring for Outside Mount Blinds and Shades

Measuring for Outside Mount Blinds and Shades

Outside mounting allows you to install blinds on windows with unique features. Use a spirit level or leveler when measuring for outside mount blind to attain a perfect straight.

Here’s how to measure for outside mount blinds and shades:

Step 1: Measure Width

Width is the left-to-right space where you intend the window treatment to cover. Use your tape to measure at least three horizontal points from one outside edge of the window casing to another. Take these measurements across the window’s top, middle, and bottom.

When measuring, overlap each side by at least an extra ¾ inch to ensure optimal light control and maximum privacy. If there are architraves, start from the outermost edges to get accurate measurements.

Step 2: Measure the Height

Height is the vertical distance from your headrail to the bottom of the headsill. Measure this distance from at least three points to the nearest ⅛ inch and record the longest distance.

Measuring for Outside-Mounted Windows With Molding or Trim

Installing blinds on windows with molding requires precise measurements that align with functionality and aesthetics.

Step 1: Measure Width

The width measurement should start from the far-left to the far-right edge. If your window has a covering with mounting brackets, deduct ¼ inch to accommodate brackets. Do this for aluminum, wood, and faux wood blinds.

Step 2: Measure the Height

Height is the vertical distance from the top edge to the bottom edge of the window trim or sill. When mounting the blinds above the window trim, make a two-inch allowance for the top edge of the trim.

Measuring for Inside-Mounted Windows With Molding or Trim

Here are a few considerations when measuring for inside-mounted windows with molding:

Step 1: Measure Width

Measure the distance between the outermost points where you’ll place the blinds. Take the width measurements to the nearest ⅛ of an inch. The blinds should reach 1½ inches beyond the window opening on each side for optimal light control.

Step 2: Measure the Height

Height is the highest and lowest vertical distance of where you’ll place the blinds. Measure the height to the nearest ⅛ of an inch.

The top of the blinds should reach 1½ inches beyond the window opening for optimal light control. If there is no sill, measure to the point where you want the blinds to hang.

Measuring for Vertical Blinds for Patio Doors

Vertical blinds are best for sliding patio doors since they fit the door’s recess. Some doors, however, tilt inwards before sliding back, leaving little room for the blind to fit. The most practical blind for tilt and slide doors is the outside mount.

Step 1: Measure Width

If you have a sliding patio door, measure at least three horizontal points and adopt the smallest measurement.

If you have a tilt and slide door, measure the width of the inside recess wall to wall. Here you will add at least 15 centimeters on each side. It will allow for an overhand around the recess as long as there are no obstructions.

Step 2: Measure Height or Drop

If you have a sliding door, measure the distance between the bottom and top of the door. You should measure at least three vertical points and adopt the smallest figure.

If you have a tilt and slide-door, measure the recess height. Add at least 10 centimeters to allow for bracket fixings and the headrail.

Measuring for Vertical Blinds for French Doors

Door blinds are outside mounted since they don’t go into a recess. The covers fit on the door’s exterior.

Step 1: Measure the Length

First, measure the length of the glass. If you have raised molding around the glass, measure from the inside of the molding to the outer edge.

Secondly, add at least two or three inches to the length of the door mount blind. This provides extra blind length for privacy and installation space.

Step 2: Measure Width

Make sure to add at least an inch to the width. If you have raised molding around the glass, measure from the inside of the molding to the outer edge. Don’t add too much to the width measurement to avoid interfering with door handles or locks.

Choosing the Right Window Blinds for Your Home

Here are some factors to consider when selecting window blinds:

  • Purpose – Consider the purpose of the room where the blinds will be installed. For example, if the room is a bedroom, you may want window blinds that provide privacy and block out light. In a living room or kitchen, you may want to let in natural light while having some privacy.
  • Style – Choose a style of window blinds that will complement the decor of your room. There are many types of blinds, including roller shades, cellular shades, Roman shades, vertical and horizontal blinds.
  • Light Control – Consider how much light you want to let in. If you wish to block out light, blackout blinds or shades would be a good choice. When looking to filter light, consider translucent or sheer shades.
  • Energy Efficiency – Some window blinds provide insulation and block out heat or cold. Cellular shades are a good choice for energy efficiency.
  • Maintenance – Look at how easy the blinds are to clean and maintain. Some blinds, like wood or faux wood blinds, may need more maintenance than others.
  • Safety & Budget – If you have children or pets, choose cordless window blinds to prevent accidents. Set a budget for the window coverings and select a style that fits within it.

Blinds and Shades Measuring Tips

Accurate measurements for blinds and shades are crucial to ensure a proper fit. Here are some tips to help you with the measuring process:

1. Use a Metal Measuring Tape

A metal measuring tape is the most reliable tool for precise measurements. Avoid using cloth or flexible tape measures, which can stretch or bend, leading to inaccurate measurements.

2. Double Check the Measurements

Double-check your measurements to ensure accuracy. Mistakes in measurements can result in blinds or shades that don’t fit or function as intended. It’s better to be thorough and measure twice than to order incorrectly sized window treatments.

3. Don’t Forget to Account for Obstructions

Take note of any obstructions within the window frame, such as window handles, cranks, or molding. Measure around these obstructions and ensure your blinds or shades fit without interfering with their operation.

4. Consider Overlapping

If you opt for an inside mount, decide how much overlap you prefer. Overlapping provides better light control and privacy. Typically, a ½ to 1-inch overlap on each side is sufficient. Take this into account when measuring the window frame.

5. Consult the Manufacturer or Retailer

Some blind and shade manufacturers or retailers provide product measuring instructions or guidelines. Consult these resources or contact their customer support to ensure correct measurements.