Square Footage Calculator
Measure area for rectangles, triangles, circles, trapezoids, and multiple rooms.
Area Results
What is the Square Footage Calculator?
The square footage calculator computes the area of rectangles, triangles, circles, and trapezoids, then converts the result into square meters and acres. Use it to size a single bedroom, plan flooring for a whole house, estimate a garden plot, or sanity-check a real-estate listing. All dimensions are entered in feet, and every calculation runs instantly in your browser with no sign-up.
How to Use
- Select a shape tab: Rectangle, Triangle, Circle, Trapezoid, or Multiple Rooms.
- Enter the required dimensions in feet (enter inches as decimals — 6 inches = 0.5 ft).
- For multiple rooms, click + Add Room to add length and width rows.
- Click Calculate Area to see square feet, square meters, and acres.
The Square Footage Formula
For any rectangular space, area is simply length times width:
Area = Length × Width
- Area — the size of the surface, expressed in square feet (sq ft)
- Length — the longer side of the space, in feet
- Width — the shorter side of the space, in feet
For other shapes, use the standard variations below:
- Triangle:
Area = ½ × Base × Height - Circle:
Area = π × Radius² - Trapezoid:
Area = ½ × (Base A + Base B) × Height
Keep every measurement in the same unit before multiplying — mixing feet and inches is the most common source of errors.
Worked Example: A 12 ft × 14 ft Bedroom
Say your bedroom measures 12 feet wide and 14 feet long:
Area = 12 ft × 14 ft = 168 sq ft
Enter 12 and 14 on the Rectangle tab and the calculator returns 168.00 sq ft, plus automatic conversions of 15.61 m² and 0.0039 acres. That one number drives most home projects — paint coverage, flooring quantities, and carpet pricing are all quoted per square foot.
How to Measure an L-Shaped Room
An L-shaped room is just two rectangles sharing an edge. Split the floor plan along the inside corner, measure each part separately, and add the areas:
- Main section: 16 ft × 12 ft = 192 sq ft
- Alcove: 6 ft × 8 ft = 48 sq ft
- Total: 192 + 48 = 240 sq ft (22.30 m²)
The Multiple Rooms tab handles this directly: add one row per rectangle and the calculator sums them for you. The same decomposition trick works for bay windows, walk-in closets, and any space with a jog in the wall.
Example: Square Footage of a Whole House
To total a floor, measure each room and add the areas together:
| Room | Dimensions | Area |
|---|---|---|
| Living room | 20 ft × 15 ft | 300 sq ft |
| Kitchen | 12 ft × 10 ft | 120 sq ft |
| Primary bedroom | 14 ft × 12 ft | 168 sq ft |
| Second bedroom | 11 ft × 10 ft | 110 sq ft |
| Bathroom | 8 ft × 6 ft | 48 sq ft |
| Total | — | 746 sq ft |
Enter these five rooms on the Multiple Rooms tab and the calculator confirms 746.00 sq ft (69.31 m²). Measure hallways and finished closets the same way and add them as extra rows.
Adding Waste for Flooring Projects
Material is always lost to cuts, breakage, and mistakes, so never buy the exact area. The standard allowance is 10% extra:
Material to buy = 168 sq ft × 1.10 = 184.8 sq ft → round up to 185 sq ft
Use 15% for diagonal or herringbone layouts and for rooms with many corners. Once you know the adjusted area, the Tile Calculator converts it into boxes of tile, and the Concrete Calculator turns square footage into slab volume for pours.
Square Footage Conversion Chart
| Unit | Equals in square feet | Example |
|---|---|---|
| 1 square yard | 9 sq ft | 6 sq yd = 54 sq ft |
| 1 square meter | 10.7639 sq ft | 100 m² = 1,076.39 sq ft |
| 1 acre | 43,560 sq ft | 0.5 acre = 21,780 sq ft |
To go the other way, divide square feet by 9 for square yards, by 10.7639 for square meters, and by 43,560 for acres. Landscaping materials are often sold by the square yard — the Mulch Calculator and Gravel Calculator handle those units for you.
What Counts in a Home's Official Square Footage
For appraisals and listings, only finished, above-grade living space counts toward gross living area: rooms that are heated, finished with permanent flooring and drywall, and accessible from inside the home. Garages, unfinished basements, attics with low ceilings, unheated sunrooms, and porches are almost always excluded — even a beautifully finished basement is usually listed separately because it sits below grade. Appraisers follow standards such as ANSI Z765, but local rules vary, so treat any listing number as approximate until you verify it yourself.
Tips for Accurate Measuring
- Measure wall to wall at floor level, keeping the tape straight and level.
- Convert inches to decimals before multiplying: 6 in = 0.5 ft, 3 in = 0.25 ft.
- Sketch the floor plan first so no closet or alcove gets forgotten.
- Measure each dimension twice — a 6-inch error over 14 feet changes the area by 7 sq ft.
- For heating and cooling estimates, pair your result with the BTU Calculator.
Frequently Asked Questions
How do I measure a room with odd shapes?
Break the room into simpler shapes like rectangles and triangles, calculate each area separately, and add them together. The Multiple Rooms tab sums as many rectangular sections as you need.
How many square feet is a 12 × 12 room?
A 12 ft × 12 ft room is 12 × 12 = 144 sq ft, or about 13.38 m². Enter 12 and 12 on the Rectangle tab to see all conversions at once.
How much extra flooring should I buy for waste?
Plan on 10% extra for straight layouts: a 168 sq ft room needs 184.8 sq ft, so round up and buy 185 sq ft of material. Use 15% for diagonal patterns or rooms with many cuts.
What is an acre in square feet?
One acre equals 43,560 square feet — roughly a square 208.7 ft on each side. The calculator converts large areas to acres automatically.
Can I use metric inputs?
Inputs are in feet. Enter your dimensions in feet and the calculator will also show the equivalent in square meters (1 m² = 10.7639 sq ft).
Does the calculator include wall thickness?
No. Enter interior dimensions if you want floor area, or exterior dimensions if you want the building footprint.
Does a garage count toward a home's square footage?
Usually not. Official living area covers finished, heated, above-grade space; garages, unfinished basements, and most porches are excluded, though a finished basement may be listed separately from the main total.