Tips for Measuring Your Window for Roller Shades

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Enjoy and embrace your creative side and personality with highly customizable window for roller shades at affordable prices. If you are ordering roller shades, you must take precise measurements to make certain they are a perfect fit for the coverage area you desire. DIY window treatment measurements can save you money if done as the professionals do it. You’ll need a metal measuring tape, a ladder, paper and a pencil and possibly a helper to measure for roller shades. Follow these measuring guidelines below for a successful roller shade installation for all different window types.

Inside Mount vs. Outside Mount

Inside Mount vs Outside Mount

You should first understand the difference between the two mounting options of inside and outside mount. An inside mount window treatment fits inside the window casing, and the brackets to hold the shade attach to the top two corners. This gives you a streamlined and clean appearance to match any decor.

Outside mount roller shades will be mounted on the wall on either side of the window casing just above the window frame. This type of mounting ensures that your shade will block out all light without any tiny gaps on the top, bottom or sides because the fabric covers more area. An outside mount is preferred if you are choosing blackout shades for a bedroom to keep it darker and promote peaceful sleep.

For an inside mount on roller shades, your window must have at least the same depth in the window casing as the depth of the chosen roller shade. You can find this in the specifications section when you are ordering or buying roller shades of any type.

Measuring for Inside Mount

Measuring for Inside Mount_

There are four easy steps for measuring a window or a door for an inside mount roller shade with proper measuring techniques.

Step 1 – Measuring the Width – Measuring your window width is done inside the casing at the top of the window opening. Measure at the top, center, and bottom, and write all three measurements down. Round down to the nearest 1/8th inch.

Step 2 – Measuring the Height – Measuring your window height is also done inside the casing from top to bottom. Take one measurement on the left, center, and right, and write all three down after rounding down to the nearest 1/8 inch.

Step 3 – Measure the Depth of The Window Casing – This is called the recess measurement or mounting depth measurement. You will measure from the glass on the window to the front of the window casing at the top, center and bottom, again measuring and rounding down to the nearest 1/8 inch.

Step 4 – Recording the Measurements – Choose the best inside mount measurements and outside mount measurements for your roller shade. Circle the smallest measurement for the width and height of your window. Then, under the measurements, note which window in your home this is for and write the size in width x height. This is the same format that should be marked on the products you are looking at.

Tips: Don’t assume two windows are the same exact size, even if they appear to be and you are covering multiple windows.  Measure each one separately. Window frame measurements differ slightly from one window to another.

Measuring For Outside Mount

Measuring Outside Mount

After determining the area you want for coverage, the process is similar to measuring for an inside mount shade, except you don’t need to measure the depth of the window casing since the shade will mount on the wall above the window.

Step 1 – Decide the Desired Coverage Area –  This part is purely up to you, but a rule of thumb is to have the width of the shade be a minimum of 1.5 inches beyond the trim on your window on each side for your roller shade dimensions. Check to see if you have enough room for an outside mount on the shades you like. You will need a clearance over the top of the window and trim and also beyond the window trim on each side on the wall. If your window has no trim work, adding 3 inches outside the window casing on all sides is recommended. This will affect your width-to-height ratio and how they appear when installed.

Step 2 – Measuring the Width – Measure 1.5 inches beyond the left and right trim at the top of the window and mark it on the wall with a pencil, or 3 inches beyond the left and right window casing if you have no trim. Measure from the left to the right mark and round the measurement to the nearest 1/8 inch. Write this measurement down as the width.

Step 3 – Measure the Height – If a window sill protrudes from the window casing, measure the height from the window sill to 3 inches over the top of the window trim or casing. This allows room for the mounting hardware or brackets. If your window sill doesn’t protrude, measure from 2 inches below the window sill to 3 inches above the window frame’s trim at the top or the window casing if you have no trim.  

Step 4- Recording the Measurements –  Be sure and record your measurements as the width x height for ordering purposes.

Tips: You can add extra coverage on the bottom and sides if you wish, and have room for it on the wall surrounding the window to ensure extra coverage. If you have an air conditioner or heater vent that will blow on the shade, it can move it slightly, so the extra fabric is extra protection when the blind is closed.

Dealing With Special Considerations

Dealing with Special Consideration

You may need to work around some instances when measuring for standard roller shades.

Window Frames with Uneven Surfaces

For both inside and outside mount roller shades, you can adjust them slightly to accommodate any uneven surface, so they will hang level and operate properly. Add a shim, which is a very thin piece of wood under the mounting hardware on the side that is smaller to adjust to the larger side.

Make sure you consider your trim and molding around your windows as stated above by adding extra coverage for outside mount shades.

The clearance requirements are needed in the depth measurement for inside mount shades in step 3 above to have enough room in the window casing for them.

Double Check Measurements

We’ve all heard the old carpenter’s saying, “Measure twice and cut once.” The same is true 

when taking measurements for window treatments. You should take each measurement twice and make certain you are reading the measuring tape correctly, as well as writing down the numbers and rounding them if necessary.

Window for Roller Shades Additional Factors to Consider


When ordering custom window treatments of any type, be aware of the window orientation and sunlight exposure. If windows face east or west, you may want to choose a thicker fabric or add a liner to your shade to make them blackout roller shades to increase energy efficiency and keep your home cooler in the summer and warmer in the winter. If your windows don’t get a lot of heat and sunlight, you may consider light-filtering roller shades to have some light when they are down but without the glare. If you have a Smart home, adding motorized roller shades to raise, lower, and adjust them with the touch of a button is a great convenience.

Thicker fabrics and liners also preserve your privacy better, which is most important in bedrooms and bathrooms, so passersby outside can’t see in your home.

Matching your fabric for your shade to your decor will help it to blend in with any setting. You can choose a bold statement color to add to a room this is otherwise neutral, or a neutral solid color for rooms with a lot of color already. You can add customization of fabric tapes to window shades or any types of embellishments you wish to make it truly your own creation.

A neutral color roller shade paired with a beautiful valance in a bright pattern adds character and depth to any area in your home. Valances also cover the mounting hardware at the top of the window for a polished appearance.


The most important aspect of securing new roller shades for your home is accuracy in measurements for your window measurements, which is even more important on the sleek inside mount style. If the shade is too small, the room will have light gaps. If the shade is too big, it won’t roll up and down as it should. Outside mount shades are a bit more forgiving, but both styles need to be mounted levelly in order for the shades to look like a professional job. 

At The Blind Broker of St. Louis, we have a highly experienced professional staff that is happy to help you with all your custom roller shades needs, and we offer a FREE in-home consultation as well. Contact us today and let us take care of all the details for you. You’ll be glad you did!

Melissa Jepsen

Melissa Jepsen

As the experienced owner of The Blind Broker St. Louis, she leads the team with a focus on quality products, personalized services, and decades of expertise in window treatments.

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