Square Footage Calculator

Measure a room's area from its length and width — in square feet and square metres. Add a price per unit for an instant material cost, and a waste allowance so you buy enough the first time.

How to use this calculator

Measure the room's length and width and pick your unit (feet or metres).
Set a waste allowance — 10% is standard, 15% for diagonal or patterned layouts.
Add a price per unit to get the material cost including waste.

Formula used

Area = Length × Width · 1 m² = 10.764 sq ft

For rectangular rooms this is simply length times width. Irregular shapes are handled by dividing them into rectangles and triangles (triangle area = ½ × base × height), then summing.

Example calculation

Worked example

A 15 ft × 12 ft room = 180 sq ft (16.7 m²). With a 10% waste allowance you'd buy for 198 sq ft.

At flooring priced 4/sq ft, that's 792 including offcuts and mistakes.

Getting area right the first time

Square footage drives nearly every material estimate — flooring, tiling, paint, carpet — so an error here multiplies through the whole project. The waste allowance is the part people skip and regret: cuts, breakage, pattern matching and mistakes mean you never use 100% of what you buy, and running out mid-job risks a dye-lot mismatch on the replacement batch.

For anything but a plain rectangle, the reliable method is decomposition: break the floor into rectangles (and the odd triangle), measure each, and add. It's more accurate than trying to average an irregular shape and easy to double-check.

Why use this calculator?

Convert between sq ft and m² automatically for mixed-unit product listings.
Bake in a waste allowance so you order enough the first time.
Get the material cost in one step with a price per unit.

Frequently asked questions

How do I calculate square footage of a room?

Multiply length by width in the same unit. A 12 × 10 ft room is 120 sq ft. For rooms that aren't rectangular, split them into rectangles, calculate each, and add the results.

How much waste should I add?

10% for standard straight layouts, 15% for diagonal installations or patterned materials that need matching, and up to 20% for complex rooms with many cuts. It covers offcuts, breakage and errors.

How do I convert square feet to square metres?

Divide by 10.764 (or multiply m² by 10.764 to go the other way). 200 sq ft ≈ 18.6 m². The calculator shows both automatically.