Free Square Footage Calculator β€” Multiple Rooms and Shapes

Calculate square footage for any room or space. Supports rectangles, triangles, circles, and L-shapes. Add multiple rooms and get a combined total.

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Rooms and Dimensions

Enter room dimensions above to see your total square footage.

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How to Measure Square Footage

Square footage is simply the area of a space expressed in square feet. For a standard rectangular room, measuring square footage is straightforward: measure the length and width of the room in feet, then multiply the two numbers together. A room that is 12 feet long and 10 feet wide has an area of 120 square feet.

For accurate measurements, use a tape measure and measure from wall to wall at the widest points. Record your measurements in feet and inches β€” this calculator handles unit conversions for you. If your room has alcoves, closets, or other protrusions, measure the overall dimensions and add or subtract sections as needed. Many people find it easiest to sketch the room on paper first and label all measurements before entering them into a calculator.

When measuring for flooring or paint, professional contractors typically recommend adding a waste factor of 10% to account for cuts, mistakes, and future repairs. This calculator includes that estimate automatically in the flooring coverage section.

Square Footage for Different Shapes

Not all rooms are simple rectangles. This calculator supports four common shapes:

  • Rectangle: The most common shape. Area = Length Γ— Width. Works for square rooms too β€” just enter the same value for both dimensions.
  • Triangle: Area = 0.5 Γ— Base Γ— Height. Useful for triangular sections of rooms, attic spaces, or dormer areas. The height must be the perpendicular height, not the slant side.
  • Circle: Area = Ο€ Γ— radiusΒ². Enter the radius (half the diameter). Useful for circular foyers, curved bay windows, or round patios. For a diameter of 10 feet, the radius is 5 feet and the area is approximately 78.5 square feet.
  • L-Shape: This calculator uses the bounding box minus cutout method. Enter the overall length and width, then the dimensions of the rectangular cutout in the corner. Area = (Total Length Γ— Total Width) − (Cutout Length Γ— Cutout Width).

For complex spaces with multiple shapes, use the "Add Room" feature to measure each section separately and let the calculator sum them automatically.

How Much Paint Do I Need?

Paint coverage varies by brand, colour, and surface type, but a standard rule of thumb is that one US gallon of paint covers approximately 350–400 square feet with one coat. This calculator uses the 400 sq ft per gallon estimate for ceiling or floor paint. For wall paint, you would need to calculate wall area separately (perimeter Γ— ceiling height).

Most rooms need two coats for full, even coverage β€” especially when switching to a significantly different colour or covering previously unpainted drywall. For two coats, double the number of gallons shown. If you are painting new drywall, consider using a primer first, which can reduce the number of finish coats needed and improve adhesion and colour vibrancy.

When buying paint, round up to the nearest quart or gallon rather than trying to buy the exact amount. Having a small amount of leftover paint is valuable for future touch-ups, and returning unused sealed cans is often possible at major retailers within a certain timeframe.

Flooring and Carpet Calculations

When purchasing flooring β€” whether hardwood, laminate, vinyl plank, tile, or carpet β€” always buy more than the measured square footage to account for waste. Professional installers typically recommend a 10% overage for simple rectangular rooms, and 15–20% for rooms with many cuts, diagonal patterns, or complex shapes. This calculator adds a standard 10% waste factor.

Flooring is sold in different units depending on the type: hardwood and laminate are typically sold by the square foot in boxes, tile is sold by the square foot or by the piece, and carpet is sold by the square yard (divide square feet by 9 to convert). Area rugs are measured in feet Γ— feet, and standard sizes often come in 5Γ—8, 8Γ—10, 9Γ—12, and larger. Measure your room and compare to standard sizes before buying an area rug to ensure proper fit and proportion.

Square Footage for Real Estate

Square footage is one of the most important metrics in real estate β€” it directly affects asking price, property taxes, and mortgage calculations. However, how square footage is measured and defined varies between listings, appraisers, and jurisdictions. In most US markets, square footage refers to finished, heated living space. Garages, unfinished basements, and enclosed porches are typically excluded from the quoted square footage, though some listings include them.

The American National Standards Institute (ANSI) has published measurement standards (ANSI Z765) for single-family home square footage, which are used by many appraisers. Under these standards, only areas with a ceiling height of at least 7 feet count towards finished area, and areas are measured to the exterior walls (not interior). This means the actual usable interior space is slightly less than the quoted square footage.

When evaluating a property's price per square foot, always verify how the square footage was measured and whether it matches public records. Discrepancies of 5–15% between listed and actual square footage are not uncommon, and they can significantly affect the true price per square foot you are paying.

Frequently Asked Questions

For a rectangular room, measure the length and width in feet using a tape measure, then multiply: Square Footage = Length Γ— Width. For example, a room that is 14 feet long and 12 feet wide has 14 Γ— 12 = 168 square feet. For non-rectangular rooms, break the space into simpler shapes, calculate each section separately, and add the results together. Use this calculator's multi-room feature to handle this automatically.

A 12Γ—12 room is 144 square feet (12 Γ— 12 = 144). This is a common bedroom size. For comparison, a 10Γ—10 room is 100 sq ft, a 15Γ—15 room is 225 sq ft, and a 20Γ—20 room is 400 sq ft. A typical US bedroom ranges from about 100 to 200 square feet, a living room from 200 to 400 square feet, and a full house averages around 2,000 square feet.

For irregular shapes, divide the area into simpler shapes (rectangles, triangles, circles) that fit within it, calculate each area separately, then add them together. For L-shaped rooms, you can also calculate the bounding rectangle and subtract the missing corner. Sketch the floor plan on paper, mark all measurements, and work section by section. This calculator supports multiple rooms and shapes so you can measure each section separately and get a combined total.

Calculate the total square footage of the area to be floored, then add a waste factor: 10% for simple rectangular rooms, 15–20% for rooms with diagonal patterns or many cuts. Multiply the square footage by 1.10 (or 1.15–1.20) to get the total amount to purchase. For example, a 200 sq ft room needs 200 Γ— 1.10 = 220 sq ft of flooring material. Always buy extra β€” running short mid-installation and needing to reorder can result in colour/lot number variations.

Square feet (sq ft) is the standard unit of area in the United States, while square meters (mΒ²) is the standard metric unit used in most other countries. 1 square meter = 10.764 square feet. To convert sq ft to sq m, divide by 10.764 (or multiply by 0.0929). To convert sq m to sq ft, multiply by 10.764. A 100 sq m apartment is approximately 1,076 sq ft β€” a size often marketed as a large 2–3 bedroom apartment in US cities.

To calculate wall area, measure the width and height of each wall and multiply: Wall Area = Width Γ— Height. Add up all four walls for the total wall area, then subtract the area of doors (typically about 21 sq ft each) and windows (typically 10–15 sq ft each). The remaining area is the paintable wall surface. Divide by the coverage rate of your paint (usually 350–400 sq ft per gallon) to find how many gallons you need per coat. Multiply by 2 for two coats, which is standard for full colour coverage.

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