How to Measure Your Windows for Retrofit Replacement
Measure your windows in minutes — then buy your own replacement windows and let our experienced installers handle the installation.
Measure Your Windows in Minutes — Save Money on Professional Installation!
Replacing your old windows? We make it easy. Learn how to measure your existing window openings correctly so you can shop for replacement windows at your preferred window dealer, manufacturer, Home Depot, or Lowe's. Then let our experienced installers handle the installation.
Three Standard Room Windows
$500
Total installation labor
One Standard Room Window
$199
Installation labor
Homeowners purchase and provide their own replacement windows. Pricing is for qualifying standard retrofit installations. Additional labor or materials, if required, will be quoted separately.
What you need before measuring
You can measure most accessible windows in just a few minutes. Record measurements in inches, including fractions down to 1/16 inch when practical. Always measure carefully — incorrect measurements can result in replacement windows that do not fit.
25-foot measuring tape
A steel tape long enough to span wide openings.
Pen or pencil
To record each measurement clearly.
Paper or measurement worksheet
Use our printable worksheet below.
Smartphone camera
Photograph each window inside and out.
Small level (optional)
Helps check that frames are plumb and level.
How to measure your windows
These are preliminary opening measurements. The final measurements used to order retrofit windows depend on the existing frame, window design, installation method, and manufacturer's specifications.
Identify your existing window frame
Before measuring, identify the existing window frame and the opening where the replacement window will fit. Retrofit windows may be installed within an existing frame, depending on the installation method. Do not assume the visible glass dimensions are the correct window ordering dimensions.
Measure the window width
Measure horizontally across the opening at three points: near the top, at the middle, and near the bottom. Record all three. The smallest width helps identify the available opening, but do not automatically order a window at this exact size.
Top 35 3/4 in · Middle 35 5/8 in · Bottom 35 11/16 in → Smallest width: 35 5/8 in
Measure the window height
Measure vertically between the top and bottom frame reference points at three points: left side, center, and right side. The window sill may be sloped, so the correct bottom reference depends on the replacement window design.
Left 47 1/4 in · Center 47 1/8 in · Right 47 in → Smallest height: 47 in
Check whether the window is square
Measure both diagonals: upper-left to lower-right, and upper-right to lower-left. If the two measurements differ significantly, the opening may be out of square and require additional installation adjustments. Send us your measurements and photos so we can help determine the next step.
Check window frame depth
Some replacement windows require a minimum installation depth. Measure the available frame depth according to the manufacturer's instructions. Do not measure through or remove glass. Window style, existing frame material, and retrofit flange design may all affect installation requirements.
Record your window measurements
Use the worksheet below to record every measurement for each window: width (top/middle/bottom), height (left/center/right), diagonals, frame depth, existing frame material, and notes. A complete worksheet helps us advise you accurately.
Blue arrows show width measurements (top, middle, bottom). Green arrows show height measurements (left, center, right). Record all three of each and use the smallest value as a reference — but do not order at that size without checking the manufacturer's instructions.
Window measurement worksheet
Print one worksheet per window and bring it with your photos.
Window Number
Room
Window Style
Existing Frame Material
Width — Top
Width — Middle
Width — Bottom
Smallest Width
Height — Left
Height — Center
Height — Right
Smallest Height
Diagonal 1
Diagonal 2
Frame Depth
Notes
Before you buy your replacement windows
Your recorded opening measurements are not necessarily the exact dimensions you should order. Retrofit window manufacturers may require specific deductions, installation clearances, frame-depth measurements, or different reference points. Window sizing requirements vary by product.
Never automatically subtract a fixed amount from your measurements or order windows using the smallest measurements without checking the manufacturer's instructions.
For best results, send your photographs and measurements to us before purchasing your windows. We can review the information and advise whether additional measurements or an on-site inspection are needed. Final window size and compatibility must be confirmed before ordering.
Watch our step-by-step window measuring guide
An instructional video demonstrating measuring window width and height, checking diagonal measurements and frame depth, recording measurements, and photographing existing windows.
Video coming soon. In the meantime, follow the illustrated steps above or call 626-313-9236 and we'll walk you through it.
Ready to replace your windows?
Text your photos and measurements for an installation estimate!
Send us:
- Your full name
- Property address
- Best contact phone number
- Number of windows being replaced
- Interior photograph of each existing window
- Exterior photograph of each existing window
- Window width and height measurements
- Photograph or product info for any windows already purchased
How can we reach you?
You buy the windows. We install them!
Why pay more when you can purchase replacement windows directly from your preferred supplier? We specialize in labor-only retrofit window installation.
One Standard Window
$199
Installation labor
Three Standard Room Windows
$500
Total installation labor
Homeowner supplies the windows. Final pricing depends on window size, accessibility, installation conditions, and any additional work required.
Frequently asked questions
Answers about measuring your windows and our labor-only installation specials.
Can I measure my windows myself?
Yes. You can collect preliminary measurements, but the exact ordering dimensions must be verified using the manufacturer's requirements.
Do I measure the glass or the window frame?
For most replacement projects, glass-only dimensions are not sufficient. The correct frame reference points depend on the installation system.
Should I subtract 1/4 inch from my measurements?
Not automatically. Follow the manufacturer's sizing instructions and required installation clearances.
Can I buy my windows at Home Depot or Lowe's?
Yes. Customers can purchase suitable replacement windows from their preferred supplier.
Do you supply replacement windows?
Our advertised specials are for installation labor. Homeowners purchase and supply their windows.
Can I send pictures before purchasing my windows?
Yes! Text your interior and exterior photographs and measurements to 626-313-9236.
What happens if my window opening is not square?
Additional adjustments or a different installation approach may be necessary. We can review your photographs and measurements.
How much does window installation cost?
Our advertised labor specials are $199 for one qualifying standard window or $500 for three qualifying standard room windows.