How to calculate floor area for a flooring quote in NZ

Steve Parker

Sep 19

5 min read

Quick answer: measure each room from its clear internal size, not the dimension chains, and total the areas by finish: timber, tile, carpet. Skirting is measured in metres, less doors and openings. Waste goes on its own line with the percentage stated. On our sample plan, gross floor area is 152.22 m²; the floor you cover is 134.77 m².

The drawings in this post are samples we made for illustration, not a real project. Every figure quoted below comes off those drawings.

A flooring quote is area times rate. Get the area wrong and the rate can't save it.

Sample: the clean plan. Chains run 11 800 × 12 900 mm to the outside of walls, and the title block shows GFA 152.22 m².

Gross floor area vs net floor area

The sample's title block says GFA 152.22 m². That is 11.8 m by 12.9 m, measured to the outside of the walls, so it takes in the 250 mm brick veneer and every 100 mm internal partition. Nobody lays carpet on top of a wall.

GFA 152.22 m²: the whole footprint, walls included. Fine for whole-house cost per m², wrong for ordering flooring.
Net floor 134.77 m²: the sum of the rooms, split by finish. This is where a flooring quote starts.

Step 1: read the plan notes before any dimension

The sample notes say two things that decide the whole measure:

Dimensions are in millimetres, to the outside of walls and the centre of partitions.
Room sizes are clear internal sizes, in metres.

So the dimension chains are not room sizes. Bed 3 sits on a 3200 mm chain across and a 4100 mm chain down, but its clear size is 2.9 × 3.8 m. The difference is the 250 mm brick veneer on one side and half the 100 mm partition on the other. The open plan works the same way: 11 800 mm overall, 11.3 m clear.

If a plan only gives chains, take the walls off before you multiply.

Step 2: measure room by room from internal sizes

Write every room down. The labelled rooms multiply out:

Open plan (kitchen, dining, living): 11.3 × 5.0 = 56.50 m²
Bed 1: 3.4 × 3.8 = 12.92 m²
Bed 2: 2.9 × 3.8 = 11.02 m²
Bed 3: 2.9 × 3.8 = 11.02 m²
Bath: 3.0 × 2.2 = 6.60 m²
Entry: 2.4 × 2.3 = 5.52 m²
Laundry: 2.2 × 2.2 = 4.84 m²

The rest carry no size label, so they come off the plan: hall 12.43 m², pantry 4.62 m², ensuite 4.32 m², WC 2.64 m², walk-in wardrobe 2.34 m². Keep the working. An area with no working behind it can't be checked.

Step 3: split the area into timber, tile and carpet

Sample: finishes marked. Timber 79.07 m², tile 18.40 m², carpet 37.30 m², net floor 134.77 m², skirting 80.88 m.

Timber, tile and carpet are different products, different rates and often different installers. One line reading "flooring 134.77 m²" hides all of that. Split it:

Timber 79.07 m²: open plan 56.50, hall 12.43, entry 5.52, pantry 4.62
Tile 18.40 m²: bath 6.60, laundry 4.84, ensuite 4.32, WC 2.64
Carpet 37.30 m²: bed 1 12.92, bed 2 11.02, bed 3 11.02, walk-in wardrobe 2.34

The three add back to 134.77 m². If yours don't match your net floor, a room is missing or counted twice. Build one finish at a time; every room gets exactly one.

Sample: layer 1, timber only. 56.50 + 12.43 + 5.52 + 4.62 = 79.07 m².

Step 4: measure skirting in metres, less openings

Skirting runs round the room, less doors, openings and joinery. It is a length, so it gets its own line. On the sample it totals 80.88 m:

Open plan 22.89 m, hall 17.38 m, entry 4.85 m, pantry 2.49 m
Bed 1 12.89 m, bed 2 10.19 m, bed 3 10.19 m

Skirting built from full room perimeters, openings left in, is over-measured at every doorway. The wet rooms carry no skirting run on the sample, so if a quote prices timber skirting through the bath, laundry, ensuite or WC, ask what it is for.

Spot the error: the bedroom that grew 2.10 m²

Same plan, one number changed. Check the bedrooms before you read on.

Sample: spot the error. One room's area does not match its size. Net floor now reads 136.87 m².

Bed 3 is labelled 2.9 × 3.8. Its area box says 13.12 m². Those two don't agree.

Sample: the answer. Bed 3 is 2.9 × 3.8 = 11.02 m², not 13.12 m². Carpet drops from 39.40 to 37.30 m².

2.9 × 3.8 is 11.02 m². The 13.12 m² is 3.2 × 4.1, taken straight off the dimension chains. That one room is over-measured by 2.10 m², which pushes carpet from 37.30 m² to 39.40 m² and net floor from 134.77 m² to 136.87 m².

The rate can be spot on and the quote still wrong. Underlay, carpet and laying all get priced on 2.10 m² of floor that isn't there.

The check takes a minute. Multiply out every labelled room and compare it with its area box. Any mismatch gets a question, in writing, before anyone signs.

Waste goes on its own line

The measured area is the floor. Waste is what you buy on top: offcuts, cuts at walls, pattern matching, breakage. Keep them apart.

Show the measured area per finish, then the waste percentage, then the order quantity.
Our wastage factors post puts tile at about 10%, plus breakage on delivery. Timber and carpet move with board direction, roll width and seam layout, so state the percentage.
If a quote only shows an order quantity, you can't tell a waste allowance from a 2.10 m² over-measure like bed 3's.

How to check a flooring quote you've been given

Checking a flooring price from a subbie or a builder? Five questions:

Is the area split by finish, with a total for each?
Does it come from clear internal sizes, not the GFA or the dimension chains?
Does every labelled room multiply out to its area?
Is skirting in metres, less doors and openings?
Is waste a separate line with its percentage shown?

A wrong area at quote stage doesn't go away. It comes back as a variation or an argument over the final invoice; our homeowner guide to building variations covers how those play out. Builders can have subbie quotes checked line by line through our builder quote review service. Measuring it yourself? Start with material takeoff from plans. Already measured and want the quantities checked before you commit? Takeoff Verification is $490 + GST per trade, back in 48 hours.

FAQ

Is floor area the same as the GFA on the plans?

No. GFA runs to the outside of the walls. On the sample, GFA is 152.22 m² and the floor you cover is 134.77 m².

Should flooring be measured to the centre of the walls?

No. Use clear internal sizes. On the sample, bed 3 is 3.2 × 4.1 on the chains but 2.9 × 3.8 clear, and using the chains adds 2.10 m².

How much waste should a flooring quote add?

It depends on finish and layout. Our wastage factors post puts tile at about 10% plus breakage; timber and carpet vary with board direction and roll width. Whatever the figure, it belongs on a separate line.

Does the floor area include under the kitchen island?

Ask. The sample open plan is measured at the full 11.3 × 5.0 m, 56.50 m², which includes the floor under the bench and island. If the flooring stops at the cabinets, that area comes out, and the quote should say which way it went.

Send us the plan and the quote

Got a flooring quote and the plan it was priced from? Send both through https://www.trueworks.co.nz/contact for a free quote check. We check the areas room by room against the drawings, per finish, skirting and waste included, and send the findings back in writing, each one cited to the sheet it came from.