Square Feet Calculator

What This Tool Does

This square feet calculator finds the area of a space — a room, a plot of land, or any surface — across common shapes like rectangles, circles, triangles, trapezoids, and sectors. It’s useful for flooring, paint, tiling, and land measurement estimates.

You can also use this Fuel Cost Calculator.

How It’s Calculated

Different shapes use different formulas:

• Rectangle: Length × Width
• Triangle (base & height): 0.5 × Base × Height
• Circle: π × (Diameter ÷ 2)²
• Trapezoid: 0.5 × (Base 1 + Base 2) × Height

Worked example (rectangle): A room measuring 12 ft × 15 ft.

• Area: 12 × 15 = 180 square feet

Worked example (triangle): A triangular plot with an 18 ft base and 10 ft height.

• Area: 0.5 × 18 × 10 = 90 square feet

For an irregular shape, break it into simpler sections (rectangles, triangles), calculate each separately, and add the results together.

Edge Cases and Special Rules

• Four side lengths alone don’t determine a quadrilateral’s area: Unlike a triangle, which is rigid given just three sides, a four-sided shape can flex into different forms with the same four side lengths but different areas. You need at least one diagonal or interior angle in addition to the four sides to calculate area accurately.
• A triangle’s three sides are enough: Since triangles are rigid, three side lengths alone (using Heron’s formula) do determine a unique area — this is different from the four-sided case above.
• Units must match before multiplying: Mixing feet and inches without converting (12 inches = 1 foot) will produce an incorrect area.
• Complex shapes need sectioning: Break an irregular room or plot into rectangles and triangles, calculate each area separately, then sum them for the total.

Square Footage vs. Cubic Footage

These measure different things, despite similar names. Square footage is a two-dimensional measurement — length × width — used for flooring, paint coverage, and land area. Cubic footage adds a third dimension — length × width × height — used for volume calculations like the amount of air in a room, or material volume for things like concrete or mulch. Entering a height value doesn’t belong in a square footage calculation at all; if height matters for your project, you likely need a volume calculation instead.

Who Uses This

• Homeowners estimating flooring, paint, or tiling material needs
• Real estate buyers and sellers comparing property sizes
• Land buyers calculating plot area before purchase
• Contractors and builders quoting costs based on square footage

Total Area vs. Total Project Cost

These aren’t the same number, and conflating them can lead to underestimating a budget. Total area (multiplied by a price per square foot) gives a baseline material or surface cost. Total project cost usually includes more — labor, material waste and cuts, preparation work, disposal, and sometimes permits — none of which scale purely with area alone. A simple area × price calculation is a useful starting estimate, not a full project quote.

FAQ

How do I calculate the square footage of a room?

Multiply the room’s length by its width, in the same unit, to get area in square feet.

Can I find the area of a shape from four side lengths alone?

Not reliably for a general quadrilateral — you also need a diagonal or an angle, since four sides alone don’t fix a unique shape.

How do I convert square feet to square meters?

Divide square feet by 10.76, or multiply square meters by 10.76 to get square feet.

What’s the difference between square footage and cubic footage?

Square footage is area (length × width); cubic footage is volume (length × width × height) — they measure different things.

How do I calculate an irregular-shaped room?

Divide it into simpler shapes like rectangles and triangles, calculate each area separately, and add them together.

Try It Above

Select your shape and enter its measurements in the square feet calculator above to get the area instantly. Add an optional price per square foot to get a baseline material cost estimate.