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What is the best way to measure for a replacement window?

I'm about to order some replacement vinyl windows and am not sure where to measure to assure the most accurate measurements. I have a brick house and was told to measure from brick to brick around the window on the outside of the house. Is this the best way? I am also aware that many times, when an order is placed, the windows will come slightly smaller. Please respond only if you have successfully measured and replaced a window. Thanks. I'm ordering my windows from Home Depot, and not from one of their sales reps (those are twice as much money). They don't come out and do measurements. They only advise on how to measure, a method I've tried in the past and was not happy with my too-small window--What good is an insulated window when there is all kinds of air passing all around it? Yeah, we caulked...a lot, but there is so much white showing around the border of the window I think it looks funny from the outside up against my brick. I just don't want my windows to come too small. A little small to make it plumb and play it safe is no big deal though. But an inch? I hired a handyman to install my windows. He just measured from drywall to drywall on the inside of the house--not very accurate, but adequate for estimates on windows . Another handyman told me to measure from brick to brick on the outside. Is that the opening? I would just tear out a window to measure the opening, but it's too cold to have an open window.

Public Comments

1. Don't take the measurements yourself. If they're wrong, you'll be responsible. Have the contractor take the measurements and you won't be liable if they come in too large or too small.


2. Brick to brick on the outisde of the house is the best way to measure. I'd also take a measurement of the window size from the outside if possible, so the window people have something else to compare the size to. You should not include the trim in either measurement.

   The window will come smaller than the opening, by about 1/2". This is to allow space to shim the window or to make sure it is plumb, level and square. If it is out of alignment, then it may leak or not operate properly.

   If you are worried you don't have the expertise to measure correctly, suggest they send a sales rep to do the measurements for you. Most reputable window companies will be willing to make sure the measurement is accurate before selling you a window.

   Also, how are you planning to install? Are you doing it yourself? Are you hiring someone to do it for you? If you are hiring someone, have that person measure for you! Installers should verify the measurements. If the company selling it to you is installing it, THEN HAVE THEM MEASURE THE OPENING! A good installer should always verify the opening for accuracy. If they don't, then call someone else who will.

   Good luck

   Brick to brick on the outside is the rough opening. Window size will come smaller so it will fit. Ask your handy man who is installing to measure accurately. If he doesn't, hire a different handy man. You can get colored caulking that is closer to your brick than white. Check a hardware store.



3. Tape measure!!!

   Just Kidding..

   Windows that are "stock sizes" will run slightly undersized.

   For example a 3'0"X4'0" window will actually be around 35 7/8 by 47 7/8. How much under varies with the manufacturer.

   If you custom order special sizes, then they will be exactly what you call for (within a 1/16th or so)

   I would under size the window by about 1/4 inch or 3/8ths to give you some room to get it in the opening. The caulking will cover that gap easily.

   You might want to order one window first as a test bed to make sure that you've accounted for all the unseen details. Or if you have the luxury, rip one out first, then you'll see the rough opening and how it relates to the brick. Some older windows have a step frame where they are larger on the outside then the inside.

   Good luck and remember you can always add material around the window frame, but you can't make them any smaller, err on the side of caution.



4. The best way is to measure the size of the rough opening, with the window out. It sounds like you were given basically sound advice, if I understand correctly. If this isn't practical, then you need to expose the window frame itself & measure it. There may be a nailing fin around the edge. Don't measure this, just the main frame.

   When ordering, be sure to specify whether your measurements are for the window frame or the opening. The standard for the industry is to make a window slightly smaller than the opening. This allows for adjustment & leveling with shims & for insulation, if needed.

   I hope this was helpful. Any good home improvement store could also give you advice.



5. On the inside of your house remove the casing from one of your windows. You will then be able to see the rough opening to measure it accurately. That's from stud to stud on the sides and the header to the plate on top and bottom. Normally 1/2" under in size is plenty for shimming but you can also check your window for square at that point. The R/O(rough opening)on the inside of the house will be same as the outside with one exception. The bottom seal is normally at a 3 degree angle to allow for water drainage but this will not change your R/O size.

   On different size windows you repeat the process.



6. Everyone gives 2 dimensional answers. This is a 3 dimensional world people. Hop fully your new windows will be as thick or thicker than the ones being removed. You have to be able to span the void from the interior framing to the brick rowlock. If your new windows are thicker you can always cut back the drywall to accommodate the additional thickness. Also if you`re purchasing a "flanged" window, the flange can be trimmed to fit. The flange is a half inch all the way around.


7. You could end up with a bunch of windows that do not fit or may look terrible when installed. It seems to me that if your handyman is not willing to provide the measurements for ordering, and stand behind them, he should not be trusted to install them. In the end, you get what you pay for in the home improvement business.

   Good luck with your windows.