Square Footage Calculator: Measure Any Space Fast

To calculate the square footage of a rectangular or square area, you need to measure its length and width in feet.

Formula: Square Footage = Length (ft) × Width (ft)

Example: If a room is 12 feet long and 10 feet wide:

Square Footage = 12 ft × 10 ft = 120 sq ft

If your measurements are in inches, you have two main options:

1. Convert inches to feet first: Divide each measurement (length and width) by 12 to convert it to feet. Then, multiply the length in feet by the width in feet.

   Length (ft) = Length (in) / 12

   Width (ft) = Width (in) / 12

   Square Footage = Length (ft) × Width (ft)

   Example: A room is 144 inches long and 120 inches wide.

   Length = 144 in / 12 = 12 ft

   Width = 120 in / 12 = 10 ft

   Square Footage = 12 ft × 10 ft = 120 sq ft

2. Calculate square inches then convert to square feet: Multiply the length in inches by the width in inches to get square inches. Then, divide the result by 144 (since 1 square foot = 12 inches × 12 inches = 144 square inches).

   Square Inches = Length (in) × Width (in)

   Square Footage = Square Inches / 144

   Example: A room is 144 inches long and 120 inches wide.

   Square Inches = 144 in × 120 in = 17,280 sq in

   Square Footage = 17,280 sq in / 144 = 120 sq ft

To calculate the square footage of a triangle, you need its base and height, both measured in feet. The height is the perpendicular distance from the base to the opposite vertex (corner).

Formula: Square Footage = 0.5 × Base (ft) × Height (ft)

Alternatively: Square Footage = (Base (ft) × Height (ft)) / 2

Example: A triangular area has a base of 10 feet and a height of 6 feet.

Square Footage = 0.5 × 10 ft × 6 ft = 30 sq ft

To calculate the square footage of a circle, you need its radius (the distance from the center to any point on the edge) in feet. If you have the diameter (distance across the circle through the center), divide it by 2 to get the radius.

Formula: Square Footage = π × Radius (ft)² (where π (pi) is approximately 3.14159)

Radius (ft)² means Radius × Radius.

Example: A circular area has a radius of 5 feet.

Square Footage = 3.14159 × (5 ft × 5 ft)

Square Footage = 3.14159 × 25 sq ft ≈ 78.54 sq ft

Calculating the total square footage of a house, especially for real estate purposes (often called Gross Living Area or GLA), involves several steps and specific guidelines:

1. Measure each room/area: Calculate the square footage of each individual room, hallway, and finished space within the house using the appropriate formulas (rectangle, triangle, etc.). Usually, measurements are taken from the exterior of the walls, or from interior wall-to-wall for individual rooms.
2. Include finished, heated, and liveable spaces: Generally, only areas that are finished (e.g., drywall, flooring, ceiling), heated, and directly accessible from the main living area are included. Basements and attics are only included if they meet these criteria and local standards (e.g., ceiling height).
3. Exclude certain areas: Garages, unfinished basements/attics, porches (unless fully enclosed and finished to the same standard as the interior), and outbuildings are typically excluded from the main GLA.
4. Two-story houses: Calculate the square footage of each floor separately and then add them together. For stairs, typically the area of the stairwell is included in the square footage of one floor only, or sometimes the footprint of the stairs is included on both levels.
5. Complex shapes: Break down irregularly shaped rooms into simpler shapes (rectangles, triangles), calculate their individual square footage, and then add them together.

Appraisers follow specific industry standards (like ANSI standards) for calculating square footage, which may differ slightly from simple room-by-room calculations. How house square footage is calculated can vary slightly based on local practices and who is doing the calculation (e.g., appraiser vs. homeowner for a project).

Calculating square footage for materials is similar to calculating room area, but with a few extra considerations:

• Flooring/Tile:
  1. Calculate the square footage of the floor area as described above (Length × Width for rectangular rooms).
  2. Add for waste: It's crucial to add a percentage for waste (typically 10-15%, sometimes more for complex layouts or diagonal tile patterns). This accounts for cuts, mistakes, and future repairs. Total Material Needed = Room Sq Ft × (1 + Waste Percentage) (e.g., for 10% waste, multiply by 1.10)
  3. Consider the size of the material (e.g., tile dimensions) to estimate the number of pieces, but total square footage is the primary calculation.
• Painting (Walls):
  1. Calculate the square footage of each wall: Wall Height (ft) × Wall Length (ft).
  2. Sum the square footage of all walls to be painted.
  3. Subtract for large openings: You can subtract the area of large windows and doors if desired, but many painters don't for simplicity, as it often balances out the need for multiple coats or detailed trim work.
  4. Check paint can coverage: Paint cans will state their approximate coverage per gallon (e.g., 350-400 sq ft). Divide your total wall square footage by the paint's coverage rate to estimate gallons needed. Remember to account for multiple coats.
• Wallpaper/Backsplash: Similar to painting, calculate the wall area. For wallpaper, also consider pattern repeat, which may require purchasing extra.

Calculating roof square footage is more complex than flat areas due to the slope (pitch) and shape of the roof.

1. Measure the footprint: Determine the length and width of the building covered by the roof (the building's footprint).
2. Account for slope: The actual surface area of a sloped roof is greater than its flat footprint. Roofers use a "pitch factor" or "slope multiplier." You can find tables for these multipliers based on the roof's pitch (e.g., a 4/12 pitch has a multiplier of around 1.054). Roof Area ≈ Footprint Area × Pitch Factor
3. Consider roof complexity: Hips, valleys, dormers, and other features add to the surface area and complexity. It's often best to break the roof into individual planes (rectangles, triangles, trapezoids), calculate the area of each, and then sum them.
4. Roofing Squares: Roofing materials are often sold in "squares." One roofing square equals 100 square feet. Number of Squares = Total Roof Sq Ft / 100

For accurate roof measurements, especially for ordering materials, it's often recommended to have a professional roofer take measurements or use specialized software.

These are two different types of measurements:

• Linear Footage (or Linear Feet): Measures length in one dimension. It's a straight line measurement. For example, the length of a piece of baseboard, a fence, or a countertop edge. It's measured in feet. You cannot directly calculate linear feet from square footage without knowing one dimension (like width). If you know the square footage and the width of a material, you can find the linear feet: Linear Feet = Square Footage / Width (in feet).
• Square Footage: Measures area in two dimensions (length and width). It tells you the amount of flat surface space. It's measured in square feet (sq ft or ft²).

Cubic footage measures volume in three dimensions: length, width, and height.

Formula (for a rectangular prism/box shape): Cubic Footage = Length (ft) × Width (ft) × Height (ft)

Example: A room is 12 feet long, 10 feet wide, and 8 feet high.

Cubic Footage = 12 ft × 10 ft × 8 ft = 960 cubic ft

Cubic footage is used for things like calculating the volume of a room for an HVAC system, the capacity of a container, or the amount of concrete needed for a slab (though concrete is often ordered in cubic yards; 1 cubic yard = 27 cubic feet).

There are two common calculations:

1. Calculating Price Per Square Foot:

   If you know the total price of an item/property and its total square footage:

   Formula: Price Per Square Foot = Total Price / Total Square Footage

   Example: A house sold for $300,000 and is 1,500 sq ft.

   Price Per Sq Ft = $300,000 / 1,500 sq ft = $200 per sq ft

2. Calculating Total Cost Based on Price Per Square Foot:

   If you know the price per square foot of a material or service and the total square footage you need:

   Formula: Total Cost = Price Per Square Foot × Total Square Footage

   Example: Flooring costs $5 per sq ft, and you need 200 sq ft.

   Total Cost = $5/sq ft × 200 sq ft = $1,000

Countertop square footage is generally calculated by measuring the length and width (depth) of each countertop section in inches, then converting to square feet.

1. Measure each section: For each piece of countertop, measure its length and width in inches.
2. Calculate square inches for each section: Length (in) × Width (in) = Square Inches.
3. Sum all sections: Add up the square inches from all countertop pieces.
4. Convert to square feet: Divide the total square inches by 144. Total Square Footage = Total Square Inches / 144

Be precise with your measurements. Some suppliers might have minimum charges or specific ways they calculate for cutouts (like sinks) or edge treatments, so always clarify with your supplier.