Figuring out how to measure window wells doesn't have to be a massive headache if you know which dimensions actually matter before you start pulling your tape measure. Whether you're looking to replace a rusted-out metal liner, install a new safety cover, or just check if your egress setup is up to code, getting those numbers right the first time will save you a lot of trips back to the hardware store.
I've seen plenty of homeowners take a quick guess, only to realize later that their new window well cover is three inches too short or doesn't sit flush against the foundation. It's one of those "measure twice, order once" kind of projects. Let's break down the process so you can get it done quickly and move on with your weekend.
Grab your tools and clear the area
Before you even worry about the numbers, you need to make sure you can actually see what you're measuring. If your window well is filled with old leaves, tennis balls the dog lost last summer, or a thick layer of silt, you're not going to get an accurate reading. Grab a shovel or a shop vac and clear out the debris around the edges where the well meets the house.
You'll only need a few basic things: * A sturdy metal tape measure (the flimsy ones are a pain for this). * A notepad and a pen (don't rely on your memory, trust me). * A level (optional, but helpful if you suspect the well has shifted). * A camera or your phone to snap a few photos of the shape.
Once the area is clear and you have your gear, you're ready to get dirty.
The big three: Width, Projection, and Height
When you're learning how to measure window wells, there are three primary dimensions you absolutely cannot skip. Everything else is just extra detail, but these three are the "bread and butter" of the job.
1. Measuring the Width
The width is the distance from one side of the well to the other, parallel to your house wall. You want to measure this at the very back of the well, right where the metal or concrete meets the foundation of your home.
Don't just measure the inside of the opening. If you're buying a cover, you usually need the outside-to-outside measurement. If you're replacing the well itself, you need to know the span of the mounting flanges. A good tip is to measure the width at the house, and then measure it again at the furthest point out. Sometimes wells "flair" out or "pinch" in over time, and knowing if it's still square will help you pick the right replacement parts.
2. Measuring the Projection
The projection is simply how far the well sticks out from the house. To get this right, place the end of your tape measure flat against the foundation wall and pull it straight out to the furthest edge of the well's rim.
If you have a rounded or "u-shaped" well, make sure you're measuring to the absolute peak of the curve. This is the measurement that most people mess up because they don't hold the tape measure perfectly perpendicular to the house. If you pull the tape at an angle, your projection will look longer than it actually is, and your new cover won't sit right.
3. Measuring the Height (or Depth)
This is where you see how deep the "hole" actually is. You'll want to measure from the top lip of the window well down to the gravel or drain at the bottom.
If you are replacing the entire well, you also need to know how much of the well is supposed to be above the ground level. Generally, you want the rim of the well to sit about 2 to 6 inches above the finished grade of your yard. This keeps rainwater from just flowing straight over the edge and into your basement.
Dealing with different shapes
Not every window well is a perfect rectangle, which can make things a bit confusing. Most are either "U-shaped," "Straight-sided," or "Circular."
For a circular or semi-circle well, you really need to focus on that center projection point. Because the sides curve back toward the house, the "width" at the house might be narrower than the widest part of the curve. It's usually best to measure the widest point wherever it occurs, even if it's a few inches away from the wall.
For rectangular or square wells, checking for "squareness" is a pro move. Measure the diagonals—from the back-left corner to the front-right corner, and then from the back-right to the front-left. If those two numbers are the same, your well is perfectly square. If they're different, your well has shifted or warped, and you might need a custom-sized cover rather than a standard one off the shelf.
Why are you measuring, anyway?
The "why" behind your project changes how to measure window wells slightly.
If you're measuring for a safety cover, you actually want to measure the exterior dimensions of the lip. You want that cover to overlap the edges so it doesn't fall through. You also need to check if your window sits higher than the well. If the window frame sticks out above the top of the well, you'll need a "stand-off" or a "bubble" cover that accounts for that extra height.
If you're measuring for an egress ladder, the depth is your most important number. Building codes usually require a ladder if the well is deeper than 44 inches. You'll need to make sure there's enough "clearance" between the window and the front of the well so a person can actually climb out in an emergency.
Common mistakes to avoid
Even if you're careful, it's easy to slip up. Here are a few things that trip people up:
- Measuring the window instead of the well: It sounds silly, but people do it. The window size doesn't always dictate the well size. Always measure the well structure itself.
- Ignoring the siding: If your house has thick siding or stone veneer, the well might be tucked slightly under it or mounted against it. Make sure you're measuring from the actual flat foundation wall if possible.
- Forgetting about the lip: Most metal wells have a 1-to-2-inch lip or flange that sits on the ground. If you're ordering a cover, you need to know if you want it to sit on that lip or inside of it.
- Assuming it's level: Old houses settle. If your well is slanted, one side might be deeper than the other. Take measurements on both the left and right sides just to be safe.
Finalizing your numbers
Once you've got your width, projection, and depth, I always suggest drawing a quick overhead "bird's eye" sketch on your notepad. Write the numbers down clearly. If you're going to a store, take that sketch and a few photos of the well with you. It's way easier to show a pro a photo of a weirdly shaped concrete well than it is to try and describe it with words.
Knowing how to measure window wells is mostly about patience. It's not a hard job, but it's a dirty one that requires a bit of precision. If you get these numbers right, your basement will stay drier, your home will be safer, and your new covers will look like they were custom-made for the place.
If you find that your well is a completely non-standard size or has been crushed by soil pressure over the years, don't try to force a standard cover to fit. At that point, you might be looking at either a custom cover or a full well replacement. But hey, at least now you have the exact measurements to tell the contractor what you need!