I round each measurement up to the nearest 1/4 foot. Then I add a percentage for waste depending on how accurate I feel my measurements are and taking into account wide doorways or diagonal walls. I'm a bit different in that I don't itemize the bid and instead propose to install the material selected in the rooms listed on the proposal. I'm rarely short on material and usually have somewhere between a part box and 2 boxes left which I'm comfortable with. Running short sucks because of the delay and often one box costs as much to ship from the supplier as a while pallet of wood.

Some people measure and round up to the nearest half or full foot. If you have long areas this can add a lot of footage. Rooms with multiple angles can be tricky to measure on site so the tendency is to go up rather than down. Some might add a higher waste percentage than others. Maybe they have experience with material that couldn't be used or want to have enough to cull through. These add up, then you round the order up to a full carton which on some materials can be 40 square feet.

I wouldn't get too hung up on square footage. Pick the person you trust the most that has a reasonable price. He should guarantee that the material he will order is sufficient to do the areas you want to do.

Figure the square footage yourself, add 10% to 15% and pick the company that is closest to your figure.

That overage % is necessary since pieces of flooring never fit the area square footage precisely. Even with sheet good flooring, overage is necessary to insure the correct installation.

It is best to have too much than too little. Again, as everyone above has stated, each installer has their own way to finagle their numbers to get the results that work for them. The MATERIAL they are working with is also going to require special consideration.

Top grade White Oak 3 3/4" solid hardwood from a reputable dealer = 5% waste....And the waste will only be because of off-cuts that are too short to put elsewhere in the install. There will be very little problem with the boards themselves (no need to cull bad boards...because there won't be any).

A low-end, "character" or "rustic" grade floor with ++ shorts from a supplier known to deal crumby stuff (ahem...LL comes to mind) then expect your waste to shoot up as high as 20%. The amount of CULLING to get the "rustic grade" piece of @#%# wood to look 'OK' (good isn't even an option for some of these low-grade floors) is HUGE. Twisted, warped, mismilled, oblong planks have to be tossed. And that can be as much as 20%. If you have weird shaped rooms we can pop that up to 25%.

And that 25% is only there because the guys you hire are CONSIDERATE and want to give you the best result possible for the floor you purchase. The rest will install what ever comes to hand, warped with knots popping out included, and then shrug when you aren't happy. They'll point to the bad wood and say, "You get what you pay for." Those are the guys that will stick to 5%-10% waste with a low-grade low-priced wood floor.

You can take your own measurements. And then add 10%. As an engineer, you are probably well suited to measure and do the math for area (I've got some clients who don't know how to find the area of a room or wall). You should be able to take some decent measurements to compare to the guys who are bidding.

And remember to take your "product of choice" into consideration when dealing with overages. There might be a reason someone wants an extra 100 feet. My guess is the material itself points in that direction.

What are the ranges we're looking at here? Is this a variance of 100' out of 500' or 100' out of 3000'?

Material will be #1 white oak. Area is around 2000 square feet. One has listed one number for square footage and another with waste (about 5% higher)......

I think Cancork hit this nail right on the head. #1 Oak can fluctuate in quality. I was looking at a floor just yesterday pondering whether it was bad #1 or decent #2. Many years ago #1 was almost interchangeable with select. When mills started sending out wood more in keeping with the minimum standard, many installers thought they'd gotten cheated. Referring to the written standards showed the mills were correct. Perhaps some have gotten worse batches of #1 and want to be compensated for buying extra wood and for the time to cull through. My sentiment is still the same. Pick the person you trust the most that has a reasonable price.

Do your homework about the various contractors you are considering using. Look for good references and high quality work and go see an example of their work in person if that is practical. Let your analytical engineering personality take over the selection process and find the right contractor.

Check the quotes carefully to make sure you understand exactly what is included in the price and what unknown extras you may be facing. If there is trim to be removed before the flooring work, whose responsibility will that be and same question about installing base and shoe molding afterwards. How about subfloor prep? Look for contractors who are concerned that the subfloor is suitable for installing your chosen material. The contract should include something about work done will follow manufacturer's installation instruction and industry standards as found in NWFA guides.

If those subjects are handled, the square footage number shouldn't concern you. That's the benefit of hiring a professional...the risk is on him. He's being paid to install the material you have chosen and you need to let him do the job. Nothing says that you can't measure the rooms yourself but don't tell the contractor the size of the rooms because that transfers the responsibility to you. If you can't find a contractor you trust to handle the install from ordering material to final presentation, then pull out your tools and do the work yourself

I've seen some pros make this comment to their clients:

"Order 5% waste up to, but not over, 100sf." I've used this as a guide line for my client's ever since = has yet to fail me. Assuming the client can measure and then CALCULATE the area+overage.

That makes sense, but then they shouldn't be charging for installing, scraping and finishing the overage, right?? After all, the wood is not the most expensive part of the process, is it?

The reason why they will still "charge" you by the amount ORDERED and not the amount LAID is this: they still have to deal with the product. Moving it, racking it, moving it, culling it, trimming it, culling it, moving it, etc.

These are all "man hours" and human sweat has a price tag. The simplest way for most people to figure out a price for their sweat = to price it for the amount ORDERED. That's the way the cookie crumbles for most of these outfits.

And the good news is, if you pay for the human sweat, you can expect something for that sweat. If there is a bad install without culling, then a repair is in order without much argument. You paid for the "handling" fees, so you expect it to be "handled".

What you are seeing is completely normal and is questionable if it is missing. If it is missing, it means someone didn't order enough flooring = massive ooopsa.

When you go to a restaurant and order a meal and only eat half of the meal, do you pay half the price or the full price of the meal? Same goes for flooring installs. If your room is 500 sf and 525 sf is ordered (additional material brought in for waste), you pay for 525 sf of material laid. All installs have waste, cuts that can not be used elsewhere. Additional material is needed to fill your install.