How to Use This Tool
Pick the shape, enter the measurements, and read the area. The flooring card adds the waste factor, because the amount to order is never the size of the room.
Area conversions are the square of length conversions
This is the single most common mistake in the whole topic. A yard is 3 feet, so a square yard is 9 square feet, not 3. A metre is 3.2808 feet, so a square metre is 10.7639 square feet, not 3.28.
It matters because carpet is frequently priced by the square yard while rooms are measured in feet. A 252 sq ft room is 28 square yards; treating it as 84 would triple the order.
L-shaped room, 20 x 15 ft with an 8 x 6 corner missing bounding box 20 x 15 = 300 sq ft missing corner 8 x 6 = 48 actual = 252 sq ft bounding box overstates by 19% at $4 per sq ft that is $192 of flooring never laid 252 sq ft = 23.41 sq m = 28.0 sq yd +10% waste = 277 sq ft to order
Most rooms are two rectangles
An L-shaped room is a rectangle with a rectangle removed, or equivalently two rectangles added. Either approach works; what does not work is measuring the longest wall in each direction and multiplying, which is the bounding box and always too large.
For anything more complex, split it into rectangles on paper, measure each, and add. Every irregular room is a set of rectangles if you are willing to draw enough of them.
The room is not the order
Flooring needs a waste allowance for cuts, and the allowance depends on the layout rather than the room: about 5 per cent for sheet vinyl, 10 for straight or offset planks and tiles, 15 for a diagonal or herringbone layout, and up to 20 for anything with a lot of edges. Ordering the exact room size is how people end up one box short with a discontinued product.
Paint is a different surface
Painting a room needs wall area, not floor area, and the two are unrelated. A 252 sq ft floor with 8 ft ceilings has roughly 500 sq ft of wall, and if you paint the ceiling too the total is over 750. Using the floor figure for a paint order is a substantial underestimate.
Quoted floor areas are not measured the same way
The square footage in a property listing usually follows a standard for gross living area, which excludes garages, unfinished basements and sometimes areas with low ceilings, and measures to the outside of exterior walls rather than the inside. It is not the number you would get by measuring the rooms, and it is not the number to order materials against.
