How Much Flooring Do I Need? A Measuring and Waste Percentage Guide

Ordering flooring is one measurement and one multiplication away from being solved - and the multiplication is the part people get wrong. Order too little and you're waiting on a second shipment that may not match. Order too much and you've tied up money in boxes you didn't need.

Here's the full math, including the waste percentage that actually applies to your layout and the one box you should deliberately keep.

Quick Answer

Measure each room's length by width, add the areas together, then add 10% for waste on a standard straight-lay installation, or 15% for diagonal, herringbone, or chevron layouts. Round the result up to whole boxes, since flooring is sold by the box - McMillan's boxes cover 19.41 sq. ft. each. Then keep one unopened box after the install as your repair kit: production runs vary slightly in color, so a plank ordered years later may not match. Unopened boxes can be returned within 90 days, which makes ordering slightly over far safer than ordering slightly under.

Step One: Measure the Space

1. Measure wall to wall, not baseboard to baseboard. Flooring runs under the baseboard or quarter round, so wall-to-wall is the true figure.

2. Multiply length by width for each rectangular area. A room 12 feet by 10 feet is 120 square feet.

3. Break irregular rooms into rectangles. An L-shaped space is two rectangles: measure each, calculate each, add them together. Same for bump-outs and alcoves.

4. Include closets, and measure stairs separately. Walk-in and reach-in closets get flooring too. Stairs are calculated per tread and riser rather than by area, and use their own components.

5. Subtract only large permanent obstructions. A fixed kitchen island or a built-in hearth comes out of the total; a refrigerator or a dishwasher does not, because flooring typically runs beneath appliances.

6. Convert inches to decimals. 10 feet 6 inches is 10.5 feet, not 10.6. Measure at a few points along each wall, since walls are rarely perfectly straight, and use the larger figure.

Two calculators on the McMillan site do this arithmetic for you: the room square footage calculator for simple rectangles, and the advanced calculator for multi-area layouts, which includes the waste factor automatically.

Step Two: Add the Right Waste Percentage

Waste isn't wasted material - it's the offcuts every installation produces. Planks get cut at walls, around doorways, and at the end of each row, and the cut-off portion is often too short to start the next row. The percentage you add depends entirely on how the floor is laid:

The math is simple: 120 square feet at 10% becomes 132 (120 x 1.10). The same room in herringbone becomes 138 (120 x 1.15).

Why 10% and not 5%: a 5% overage leaves almost no margin for a mis-cut, a damaged plank in a box, or a room that measured slightly short. On a 1,000 square foot job, the difference between 5% and 10% is about 50 square feet - roughly two and a half boxes, and the difference between finishing the job and stopping halfway through the last room.

Step Three: Round Up to Full Boxes

Flooring is sold by the box, not the square foot, so the final step is converting your total into box count. McMillan's boxes cover 19.41 square feet each and weigh about 47 pounds. Divide your waste-adjusted square footage by the box coverage and round up - always up, never down.

Using the example above: 132 square feet divided by 19.41 equals 6.8 boxes, so you order 7. That rounding typically adds a little more material on top of your waste percentage, which is a feature rather than a problem. McMillan's checkout handles this rounding automatically, so the quantity you see is the quantity that will actually cover the room.

Why the Leftover Box Matters More Than You Think

This is the part most measuring guides skip, and it's the reason to be relaxed about ordering slightly over.

Flooring is manufactured in production runs, and color can vary subtly between them. Planks from the same run are matched to each other; planks ordered two years later come from a different run and may be a shade off - close enough to look like a mistake rather than a match. If a plank is ever damaged by a dropped pan or a furniture accident, a spare box from your original order is a perfect match. A fresh order is a gamble.

The practical rule: keep one unopened box in a closet or garage after the install, stored flat and indoors. It is the cheapest insurance available on a 25-year floor. Anything beyond that spare box can be returned unopened within 90 days, so ordering a little generous costs you nothing but a return shipment - while ordering short costs you a delay, a second freight charge, and a possible color mismatch.

Ordering for Multiple Rooms

• Same floor throughout: add all room areas together first, then apply the waste percentage once to the combined total. Applying it room by room over-orders slightly, since offcuts from one room are usable in the next.

• Different floors per room: calculate each product separately, each with its own waste percentage.

• Order it all at once. Material bought in a single order comes from the same production run and matches exactly. Splitting a project across two orders is the most common cause of visible color variation between rooms.

• Don't forget accessories. Transition moldings, stair nosing, and quarter round are counted per doorway and per stair, not by square footage. Walk the project and count them before checking out.

Frequently Asked Questions

How much extra flooring should I order for waste?

Add 10% to your measured square footage for a standard straight-lay installation, and 15% for diagonal, herringbone, or chevron layouts, or for rooms with many corners and doorways. Then round up to whole boxes. The overage covers cuts at walls and doorways, staggering offcuts, and the occasional damaged plank - and leaves you a spare box for future repairs.

How do I calculate how much flooring I need?

Measure each area's length and width wall to wall, multiply to get square feet, and add the areas together, breaking irregular rooms into rectangles. Include closets, subtract only large permanent fixtures like a kitchen island, then add 10% for waste (15% for patterns) and round up to full boxes. McMillan's square footage calculators do the arithmetic, including the waste factor.

How many square feet does a box of flooring cover?

McMillan's boxes cover 19.41 square feet and weigh roughly 47 pounds each. To find your box count, divide your waste-adjusted square footage by 19.41 and round up. A 132 square foot total works out to 6.8 boxes, so you would order 7. Checkout rounds to whole boxes automatically.

What happens if I order too much flooring?

Keep one unopened box as a repair kit - production runs vary slightly in color, so a plank ordered later may not match your floor. Beyond that, unopened boxes can be returned within 90 days. This asymmetry is why ordering slightly over is much safer than ordering short, which risks a delay, a second freight charge, and a color mismatch.

The Bottom Line

Measure wall to wall, add the rooms together, add 10% (or 15% for patterns), round up to whole boxes, and keep one box back. That sequence takes ten minutes and eliminates the two failure modes that actually cost money: running short mid-install, and having no matching material when a plank needs replacing five years from now.

Room Square Footage Calculator →

Advanced Square Footage Calculator →

Read: How Much Does LVP Flooring Cost? →

Read: How to Transition Between Flooring Types →

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Accurate measurements mean better planning, smarter purchasing, and a flooring installation that goes off without a hitch. If you need help calculating your space or choosing the right flooring material, the team at McMillan Floors is here to help.