If you're replacing windows, one of the first decisions you'll face is choosing between single hung vs double hung windows. While they may look similar, the differences can impact cost, maintenance, ventilation, and long-term...
Measuring windows incorrectly is one of the most common (and expensive) mistakes homeowners and property owners make during a replacement project.
Even small errors can lead to poor fit, air leaks, delays, or having to reorder entirely.
If you’re planning a window replacement, getting accurate measurements upfront can save you time, money, and frustration.
In this guide, we’ll walk you through exactly how to measure your windows the right way — so you can move forward with confidence.
How to Measure Windows for Replacement (Quick Steps)
- Measure width at the top, middle, and bottom
- Use the smallest measurement
- Measure height on the left, center, and right
- Measure the depth of the window frame
- Record all measurements carefully
Why Accurate Window Measurements Matter
Accurate measurements ensure:
- A proper fit
- Better energy efficiency
- Faster installation
- Fewer costly mistakes
Incorrect measurements are one of the most common reasons window replacement projects get delayed or require rework.
Tools You’ll Need
- Tape measure (metal preferred)
- Notepad or phone
- Pencil
- Ladder (if needed)
Step 1: Measure the Width
Measure the width of the window opening at three points:
- Top
- Middle
- Bottom
👉 Always use the smallest measurement.
Not Sure Your Measurements Are Right?
We measure windows every day — and we know exactly where mistakes happen.
If you want to be 100% confident before ordering or installing, we can handle the measurements for you.
👉 Schedule a window measurement
Step 2: Measure the Height
Measure height in three places: 
- Left
- Center
- Right
👉 Again, use the smallest measurement.
Step 3: Measure Window Depth
Measure how deep the window frame is—from the inside edge of the frame to the glass.
Most replacement windows require at least 3 1/4 inches of depth, but older homes and multifamily properties can vary.
Common Measurement Mistakes
Avoid these common issues:
- Measuring only once
- Using the largest number instead of the smallest
- Measuring trim instead of the actual opening
- Ignoring uneven frames
These issues are especially common in older Denver homes and multifamily properties where openings may not be perfectly square.
Retrofit vs Full Window Replacement
Before ordering windows, it’s important to understand your options:
Retrofit (Insert) Windows
- Installed within the existing frame
- Faster and more cost-effective
- Best when the frame is still in good condition
Full Window Replacement
- Entire window system is replaced
- Better for older, inefficient, or damaged windows
- Improves energy performance and long-term value
Should You Replace the Glass or the Entire Window?
This is one of the most common — and most misunderstood — decisions property owners make.
The right decision isn’t just about cost — it’s about performance, efficiency, and long-term ROI.
While replacing glass can seem like a quick fix, the right approach depends heavily on the type and condition of your existing windows.
When a Glass (or Glass Pack) Replacement May Make Sense
For newer vinyl windows, it’s sometimes possible to replace the insulated glass unit (glass pack) instead of the entire window.
This can be a good option when:
- The frame is in good condition
- The issue is limited to failed or broken glass
- You need a faster solution during a unit turn
When Full Window Replacement Is the Better Investment
In many cases — especially with older properties — full window replacement delivers better long-term value.
This is often true when:
- Windows are older wood or single-pane units
- Frames are deteriorating or inefficient
- You want improved energy efficiency
- You’re upgrading the property to stay competitive in the market
New windows can:
- Lower heating and cooling costs
- Improve sound insulation
- Increase renter satisfaction
- Enhance curb appeal and property value
What About Older or Wood Windows?
If your property has older wood windows or single-pane glass, full replacement is typically the better path.
In these cases, we often recommend working with a specialized glass provider if repair is the goal — or moving directly to a full window upgrade for better performance.
When to Measure Windows Yourself vs When to Call a Professional
Measuring windows yourself is a great first step — especially if you’re planning a project or getting rough pricing. But there’s a difference between initial measurements and final measurements used for ordering windows.
Knowing when to handle it yourself — and when to bring in a professional — can help you avoid costly mistakes.
When You Can Measure Windows Yourself
You can confidently measure windows yourself when:
- You’re in the early planning stage
- You want a rough estimate for budgeting
- You’re comparing replacement options
- You’re measuring standard, newer windows
- Frames appear square and in good condition
👉 In these cases, your goal is to get close enough to make decisions, not place a final order.
When You Should Call a Professional
It’s best to bring in a professional when:
- You’re ready to order replacement windows
- The home is older or has wood/single-pane windows
- Frames may be uneven, damaged, or out of square
- You’re unsure if it’s a retrofit vs full replacement
- You’re managing multiple units or a larger project
Even small measurement errors can lead to:
- Poor fit
- Air leaks
- Delays and reordering
- Increased installation costs
👉 At this stage, accuracy matters — and professional measurements help eliminate risk.
A Simple Rule to Follow
- DIY measurements = planning and estimating
- Professional measurements = ordering and installation
Why This Matters for Your Project
Window replacement isn’t just about size — it’s about:
- Fit and performance
- Energy efficiency
- Long-term durability
Getting measurements wrong at the ordering stage can delay your project and increase costs.
Need Help Verifying Your Measurements?
If you’re not sure your measurements are accurate — or you’re deciding between repair, retrofit, or full replacement — it’s worth getting a second opinion.
👉 Book a Property Review and we’ll help you confirm measurements, evaluate your windows, and plan your project the right way.
Window Measurement Services in Denver
At ImproveSource, we work with homeowners, property managers, and real estate investors to:
- Accurately measure windows
- Evaluate repair vs replacement options
- Reduce unnecessary costs
- Plan upgrades that improve property value and performance
Stop Guessing Your Measurements
Accurate measurements are the difference between a smooth installation and a costly mistake.
We’ll measure your windows, recommend the right fit, and give you a clear, no-surprise quote.