Area 1
Total Area
Square Feet
120.00
Square Yards
13.33
Square Meters
11.15
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Square Footage Calculation Guide
Measurement techniques, formulas for all shapes, and waste factors for material ordering.
How to Calculate Square Footage
Square footage = Length × Width (in feet). For irregular shapes, break the area into rectangles, calculate each, and add them together.
- Rectangle: Length × Width
- Triangle: (Base × Height) ÷ 2
- Circle: π × Radius² (3.14159 × r²)
- L-shaped room: Split into 2 rectangles, calculate each, add together
- Converting: 1 sq yard = 9 sq ft | 1 acre = 43,560 sq ft
Always measure in the same units. If you measure in inches, divide each dimension by 12 before multiplying, or divide the result by 144.
Key Takeaways
- Rectangle: Length × Width
- For irregular rooms: split into rectangles
- 1 sq yard = 9 sq ft | 1 acre = 43,560 sq ft
How to Measure Rooms for Construction Projects
Measure at the longest and widest points of each rectangular section, rounding up to the nearest inch for material ordering.
- Walls: Measure at floor level (base of walls), not at the top
- Closets/alcoves: Include in the total room area if being floored/finished
- Wall area (for paint): (Perimeter × Ceiling Height) – doors – windows
- Ceiling area: Same as floor area (Length × Width)
- Always round up: Materials come in standard sizes — better to have a little extra
Key Takeaways
- Measure at floor level for accuracy
- Include closets/alcoves if being finished
- Always round up for material ordering
Square Footage for Material Ordering
Add waste factor to square footage before ordering materials: 5–10% for standard installations, 15–20% for diagonal or pattern layouts.
- Flooring: Add 10% waste (15% for diagonal/herringbone)
- Tile: Add 10–15% waste (breakage + cuts)
- Paint: 1 gallon per 350–400 sq ft (per coat)
- Drywall: Add 10% waste for cuts around doors/windows
- Insulation: Add 5–10% waste
For multi-room projects, calculate each room separately then add totals. Different rooms may need different materials or waste factors.
Key Takeaways
- Standard waste factor: 10% for most materials
- Diagonal layouts: 15–20% waste
- Calculate rooms separately, then sum totals
How to Use This Calculator
Choose your shape
Select the shape that matches your space: rectangle, triangle, circle, L-shape, or trapezoid. Most rooms are rectangles. For complex spaces, add multiple shapes and combine them.
Measure and enter your dimensions
Grab a tape measure or laser distance tool. Input length and width (for rectangles), base and height (triangles), or radius (circles). Toggle between feet and inches as needed.
Add multiple areas for irregular rooms
Click "Add Another Area" to break L-shaped or multi-room spaces into simple shapes. Each area can use a different shape. The calculator keeps a running total automatically.
Review results and convert units
See your total in square feet, square yards (for carpet orders), and square meters (for metric specs). Add 10–15% waste factor before ordering materials.
Square Footage Formulas
Rectangle: Area = Length x Width
Triangle: Area = Base x Height / 2
Circle: Area = π x Radius²
Trapezoid: Area = (Side A + Side B) / 2 x HeightWhere:
- Length, Width
- = Measurements in feet (or inches, divided by 12)
- π
- = 3.14159 (Pi)
- Sq Yards
- = Square feet ÷ 9
- Sq Meters
- = Square feet x 0.0929
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Frequently Asked Questions
How do I calculate square footage?
For a rectangle, multiply length x width. For example, a 12 ft x 10 ft room = 120 sq ft. For triangles, use base x height / 2. For circles, use π x radius². For L-shaped rooms, divide the space into two rectangles and add their areas together.
How do I convert square feet to square yards?
Divide square feet by 9 to get square yards. There are 9 square feet in 1 square yard (3 ft x 3 ft = 9 sq ft). For example, 180 sq ft ÷ 9 = 20 sq yd. This conversion is commonly used when ordering carpet, which is typically priced per square yard.
How do I convert square feet to square meters?
Multiply square feet by 0.0929 to get square meters. For example, 200 sq ft x 0.0929 = 18.58 sq m. Alternatively, 1 square meter equals approximately 10.764 square feet. This conversion is useful for international material orders and metric specifications.
How do I measure a room that is not a perfect rectangle?
Break the room into simple shapes: rectangles, triangles, or semicircles. Measure each section separately, calculate the area of each, and add them together. For an L-shaped room, divide it into two rectangles. For rooms with bay windows, add a rectangle for the main room plus a trapezoid for the bay area.
How much flooring do I need for a room?
Calculate the room area in square feet, then add 10% for waste (15% for diagonal installations). For example, a 150 sq ft room needs about 165 sq ft of material. Always round up to the nearest full box or roll. Check the coverage per box listed on the flooring packaging.
What is the square footage of common room sizes?
Common room sizes: 10x10 = 100 sq ft (small bedroom), 12x12 = 144 sq ft (average bedroom), 15x20 = 300 sq ft (living room), 10x12 = 120 sq ft (kitchen), 5x8 = 40 sq ft (bathroom). A standard 2-car garage is typically 20x20 = 400 sq ft.
How do I calculate square footage with feet and inches?
Convert inches to a decimal fraction of a foot first. Divide the inches by 12 and add to the feet. For example, 12 ft 6 in = 12.5 ft, and 14 ft 3 in = 14.25 ft. Then multiply: 12.5 × 14.25 = 178.13 sq ft. Never treat the inches as a decimal (12.6 × 14.3 is wrong).
How much waste should I add when ordering flooring?
Add 10% waste for standard straight-lay installations. Add 15% for diagonal, herringbone, or chevron patterns. For rooms with many cuts (small rooms, lots of angles), go with 15% regardless of pattern. Always round up to full boxes.
How do I calculate square footage for paint?
For paint, you need wall area, not floor area. Multiply the room perimeter (total wall length) by ceiling height. A 12×14 ft room with 8 ft ceilings: perimeter = 52 ft × 8 ft = 416 sq ft of wall area. Subtract ~20 sq ft per door and ~15 sq ft per window. One gallon covers about 350–400 sq ft. Use our paint calculator for exact quantities.
Is square footage measured from interior or exterior walls?
It depends on the purpose. Real estate listings use exterior dimensions per ANSI Z765-2021, which includes wall thickness. Material estimates (flooring, tile, carpet) use interior wall-to-wall measurements since that is the actual surface you are covering.
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