How much extra flooring should I buy?

For a straight layout in a simple room, around 10% over the measured area is a common starting point. Rooms with many cuts, diagonal layouts or patterned planks usually need more. The allowance here is adjustable because the right number depends on your room, not on a universal rule.

Where do I find the coverage per box?

It is printed on the end of the carton, usually as square feet per box or square metres per box, sometimes alongside the number of planks. If a retailer lists it online, check it against the physical box, because it can differ between finishes of the same range.

Does the calculator account for the underlay?

No. This calculates the flooring itself. Underlay is sold in rolls with their own coverage, so it needs its own figure rather than an assumed ratio.

Why is the leftover different from what I expected?

Leftover here is measured against your planned quantity, which already includes the waste allowance. It is what remains after the cuts you have budgeted for, not the difference between the boxes and the bare floor area.

Flooring Calculator

Measure the rooms, tell us what one box covers, and get the number of boxes to buy — with the waste allowance, the leftover and the cost all shown separately.

Units

Feet & inches

Metric

Switching units keeps your measurements. Nothing is reset.

Areas

Shape

Length

Width

Diagram, not to scale

Your flooring

Coverage per box

Printed on the carton, usually as square feet per box.

10% is a common starting point for a straight layout in a simple room.

Offcuts, breakages, pattern matching and the occasional damaged piece all mean you use more material than the bare area. Keeping a few spare pieces for future repairs is also normal.

This is a planning allowance, not a rule. Adjust it for your layout, your material and your own tolerance for a second trip to the store.

Price per box

Cost uses the price you enter. This product never shows invented market prices.

Your result appears here

Enter your measurements to see how much material to buy.

How to use this calculator

1
Measure each room at its widest points and enter the length and width. Use the feet and inches boxes exactly as you read them off the tape — there is no need to convert anything.
2
Add a second area for a hallway, a closet or the other half of an L-shaped room. Each area is totalled before any waste is applied.
3
Find the coverage on the carton — most flooring prints square feet per box on the end label — and enter it. This is the one number that has to come from the product you are actually buying.
4
Adjust the waste allowance if your layout is diagonal, patterned or full of awkward cuts, then add your local price per box if you want a cost estimate.

A worked example

A living room of 12 ft × 15 ft plus a 4 ft × 10 ft hallway, with a 10% waste allowance, boxes covering 23.5 ft² and a price of $45 per box:

Add the areas together
180 ft² + 40 ft²220 ft²
Add the waste allowance
220 ft² × 1.1242 ft²
Divide by the coverage of one package
242 ft² ÷ 23.5 ft²10.3
Round up to whole packages
round up 10.311
Coverage you are buying
11 × 23.5 ft²258.5 ft²
Multiply by your price
11 × 45495
You will need
11 boxes

This example is produced by running the calculator above, so it always matches what the tool does.

The formula

Total area is the sum of every area you entered. The planning quantity is that total multiplied by one plus the waste percentage. Dividing by the coverage of one box gives a fractional box count, which is always rounded up, because a part box cannot be bought. Purchased coverage is the whole box count multiplied by the coverage per box, and the leftover is what that leaves beyond your planned quantity.

Getting a good estimate

Measure the widest points, including under the doors

Floors run into doorways and under radiators. Measure the full rectangle rather than the visible floor, then add doorway thresholds as small separate areas if they are significant.

Coverage differs between boxes of the same product

Plank length and box count vary by batch and by finish. Use the figure on the boxes you are actually buying, and check it again if you go back for more.

Diagonal and patterned layouts waste more

A straight layout in a plain rectangular room is the cheapest case. Diagonal installation, herringbone, or a strongly patterned plank that has to be matched all push the waste allowance higher.

Keep a spare box, not a spare plank

Replacing a damaged board years later is far easier if you kept a full box from the same batch. That is often a better reason to round up than the cutting waste itself.

Common questions

How much extra flooring should I buy?: For a straight layout in a simple room, around 10% over the measured area is a common starting point. Rooms with many cuts, diagonal layouts or patterned planks usually need more. The allowance here is adjustable because the right number depends on your room, not on a universal rule.
Where do I find the coverage per box?: It is printed on the end of the carton, usually as square feet per box or square metres per box, sometimes alongside the number of planks. If a retailer lists it online, check it against the physical box, because it can differ between finishes of the same range.
Does the calculator account for the underlay?: No. This calculates the flooring itself. Underlay is sold in rolls with their own coverage, so it needs its own figure rather than an assumed ratio.
Why is the leftover different from what I expected?: Leftover here is measured against your planned quantity, which already includes the waste allowance. It is what remains after the cuts you have budgeted for, not the difference between the boxes and the bare floor area.