Floor Area Calculator
Add rooms, type length × width. Get total square footage, acres, and optional cost.
How to use
Add one row per rectangular room or rectangular section. For L-shaped or T-shaped rooms, split them into rectangles and add each as a separate row. The calculator sums everything.
- Pick your input unit (feet or metres).
- For each room, type its length and width. Optionally give it a name for the plan view.
- Add more rooms with the + Add room button. Up to 12 rooms supported.
- Type a cost per square foot/metre to get a total cost estimate — useful for flooring quotes, paint, or rent calculations.
Reviewed 6 June 2026 · methodology cited
About this calculator
Floor area — square footage in the US and Canada, square metres in most of the rest of the world — is the most common building measurement. It drives rent and lease pricing, mortgage and real estate listings, flooring and paint quotes, property tax assessment, and pretty much any cost-per-foot or cost-per-metre estimate in construction and real estate.
This calculator sums any number of rectangular rooms into a single total area. For L-shaped or T-shaped rooms — or for a full floor plan with kitchen, living room, bedrooms, and hallways — you split each space into the rectangles that make it up and add a row per rectangle. The calculator handles up to twelve rectangles per session, which covers most residential floor plans. For larger commercial work, save the link to share or extend a session.
The math behind it
Area of a rectangle = length × width. Total floor area = sum of each rectangle's area. The unit conversions: 1 ft² = 0.0929 m² = 1/43,560 acre = 1/9 yard². So a 1,200 ft² apartment is 1,200 × 0.0929 = 111.5 m², or 1,200 ÷ 43,560 = 0.0276 acres.
Worked example — a 1-bedroom apartment: living room 16 × 14 = 224 ft², kitchen 10 × 12 = 120 ft², bedroom 12 × 14 = 168 ft², bathroom 8 × 6 = 48 ft², hallway 4 × 10 = 40 ft². Total = 600 ft² = 55.7 m². At $2.50/ft² for new vinyl plank flooring, the materials cost is 600 × $2.50 = $1,500 — though labour, underlayment, and trim usually add another 50–100 percent.
For cost estimates, the per-square-foot rate varies enormously by region and finish. Residential carpet runs $2–6/ft²; vinyl plank $2–8/ft²; engineered hardwood $4–12/ft²; site-finished hardwood $8–20/ft²; tile $5–15/ft² installed. Paint is usually $0.50–2/ft² for materials, more for labour. Always confirm with a local supplier or contractor; this calculator does the multiplication, not the pricing.
Common floor-area applications
| Application | Typical area | Use case |
|---|---|---|
| 1-bedroom apartment | 500–800 ft² | Urban rental, real estate listings |
| 2-bedroom apartment | 800–1,200 ft² | Common condo/apartment size |
| Small house (3-bed) | 1,200–1,800 ft² | Typical starter home |
| Mid-size house | 1,800–2,800 ft² | Suburban detached single-family |
| Large house | 2,800–4,500 ft² | Custom build, executive home |
| Office (small) | 500–2,000 ft² | Single tenant, co-working pod |
| Standard retail unit | 1,000–3,000 ft² | Strip-mall storefront |
| Restaurant (small) | 1,500–3,500 ft² | Café or quick-service |
| Warehouse bay | 5,000–20,000 ft² | Industrial / light industrial |
| Single-car garage | 200–280 ft² | Detached or attached |
| Double-car garage | 400–576 ft² | Typical 20 × 22 to 24 × 24 |
| Standard parking stall | 162 ft² | 9 × 18 ft (varies by jurisdiction) |
Multi-room and L-shaped plans
Most rooms are not perfectly rectangular. The trick is to split a non-rectangular room into rectangles using imaginary lines. An L-shaped living room becomes two rectangles: the main rectangle plus the alcove. A T-shaped kitchen becomes the long bar plus the breakfast nook. Add each rectangle as its own row, give them names for the plan view, and the total comes out correct.
For circular spaces (rotundas, bay windows with curved walls), use π × r² for the circle and convert to a rectangle of equivalent area. For triangular spaces (under a stair, attic), use base × height ÷ 2. The Triangle Calculator and Cylinder Volume Calculator on this site cover those shapes; this one is purely rectangular.
When estimating cost, always check whether the per-square-foot price you were quoted includes labour or not. Flooring quoted at $3/ft² is usually materials-only; add 50 percent for installation if the supplier doesn't say otherwise. For rent, the per-square-foot figure usually includes everything, but verify whether common areas (lobby, gym) are counted in or out.
Frequently asked questions
How do I calculate square footage of an L-shaped room?
Split the L into two rectangles with an imaginary line, then add each rectangle as its own row. For example, an L-shaped living room with a 14 × 16 main area plus a 6 × 8 alcove becomes two rows: (14, 16) = 224 ft² and (6, 8) = 48 ft². Total = 272 ft². The plan view shows both rectangles labeled.
What about closets, hallways, and stairs?
Real estate listing area usually includes finished, heated, interior space — so hallways and walk-in closets are in; unfinished basements, garages, decks, and the stair footprint are out. Code-defined Gross Floor Area (used for zoning) includes more, sometimes everything inside the exterior walls. Always check the convention you are reporting to.
How many square feet are in a square metre?
One square metre equals 10.7639 square feet. So a 100 m² apartment is 1,076 ft². Conversely, 1 ft² = 0.0929 m². The conversion factor is (1 m ÷ 0.3048 m/ft)² = 10.7639 because area scales as the square of the length conversion.
How many square feet are in an acre?
43,560 square feet equal one acre. This is the value to divide by when converting building footprint or lot size to acres. A typical American football field including end zones is about 57,600 ft² or 1.32 acres. A standard suburban lot of 7,500 ft² is 0.17 acres.
Is this calculator accurate for property tax or appraisal?
It gives the arithmetic correctly, but property tax assessment uses jurisdiction-specific rules about what to include — finished vs unfinished space, garage, basement, partial-height rooms — that this calculator does not enforce. Use it for a quick estimate; consult a licensed appraiser or your local assessor for an authoritative figure.
Can I include circular or triangular spaces?
Not directly — this tool sums rectangles only. For a circular space, compute π × r² with the Cylinder Volume Calculator (which shows the cross-sectional area too), then add an equivalent-area rectangle here. For triangular spaces, compute base × height ÷ 2 with the Triangle Calculator and add an equivalent rectangle here.