Square Footage Calculator
Calculate area and material estimates
Square Footage Calculator tool
Rooms
Square Footage Calculator: key facts
- What it does
- Calculate area and material estimates
- Category
- Other Calculators
- Cost
- Free, with no account, sign-up, or install.
- Your data
- Runs entirely in your browser — the files and text you enter are never uploaded to a server.
- Last reviewed
- . Report an incorrect result.
What this tool is for
Whether you are buying flooring, ordering paint, or listing a property, you need the area of a space in square feet — and rooms are rarely a single simple rectangle. This calculator totals the area across multiple rooms, handles rectangular, circular, and triangular shapes, and even estimates the flooring and paint you will need.
Homeowners and renters measure rooms for renovations, real-estate agents total a floor plan, and DIYers size a project before buying materials. Adding rooms one by one and summing them means an L-shaped space or a whole apartment is handled in one calculation, with a built-in material estimate to take to the store.
How to use the Square Footage Calculator
- Choose your units: feet, meters, or yards.
- Add each room, pick its shape (rectangle, circle, or triangle), and enter its dimensions.
- Read the total area across all rooms, plus the perimeter of rectangular rooms.
- Use the flooring and paint estimates, which add waste and coats, when buying materials.
Multiple areas, and the material estimates
Each area you add is computed by its own shape formula — rectangles multiply their sides, circles use pi times radius squared, triangles take half base times height — and the results are summed. Adding several sections is the intended way to handle an irregular space: break it into shapes you can measure and let the tool total them.
Two material estimates are derived from the total. Flooring adds 10% for cuts and waste, matching standard trade practice. Paint doubles the area, on the assumption of two coats, which is what most surfaces need for even coverage over a previous colour.
Both are starting points rather than orders. Actual coverage depends on the product, and paint tins state a spread rate per litre that varies considerably between primers, emulsions, and exterior finishes.
- A 200 square foot total suggests 220 square feet of flooring to allow for cuts.
- The paint figure for the same space is 400 square feet of coverage, being two coats.
- An L-shaped room splits naturally into two rectangles — 12 by 10 and 8 by 6 — totalling 168 square feet.
What the Square Footage Calculator gets right
- It sums multiple rooms of different shapes in one go, so an irregular layout does not need separate calculations.
- It estimates materials — flooring with a 10% waste allowance and paint for two coats — turning area into a shopping list.
- It supports feet, meters, and yards and reports rectangular perimeters alongside area.
- It calculates locally with no account.
Measuring properly, and what gets counted
Measure the space rather than working from a plan, since drawings are frequently idealised and rooms are rarely square. Take each dimension at more than one point: a wall that measures 3.6 m at one end and 3.65 m at the other is normal, and using the larger figure keeps you from ordering short. A laser measure is quicker and more accurate than a tape over long runs.
What counts as floor area depends on why you are asking. For flooring, subtract fixed fittings and built-in units but include the space under furniture. For paint, work in wall area rather than floor area — perimeter times height — then subtract doors and windows, though many decorators leave openings in as an allowance for waste.
Be careful with published property floor areas, since the definitions differ by market and by convention: gross internal area, net internal area, and whether balconies, garages, or loft space are included all vary. A figure quoted in a listing is not necessarily measuring the same thing you are.
Frequently Asked Questions
How do I calculate the square footage of a room?
For a rectangular room, multiply length by width. For circular or triangular spaces the formulas differ, which is why this calculator lets you pick the shape. Add each room and it totals the combined area for you.
How much extra flooring should I buy for waste?
A common rule is to add about 10% for cuts, mistakes, and future repairs, which is exactly the allowance this calculator's flooring estimate uses. For complex layouts or diagonal patterns, you may want to add more.
How do I measure an L-shaped or irregular room?
Divide it into simple rectangles, add each as a separate room here, and the calculator sums them. Any outline can be broken into rectangles, circles, and triangles this way to get an accurate total.
Why does the paint estimate assume two coats?
One coat rarely gives even, full coverage, so painters typically apply two — which is why the paint estimate doubles the area. If you are using a primer or a one-coat paint, you can scale the figure down accordingly.
