CalcRover

Area Calculator

Pick a shape and enter its dimensions — all in the same unit — to get the area with the formula applied step by step. For measuring rooms and floors in feet, the square footage calculator is the remodel-focused version of this page.

All dimensions in the same unit — the answer is in that unit squared.

Area formulas

The four everyday shapes cover most homework and DIY measuring. Triangle height means the perpendicular distance from the base to the opposite corner — not the slanted side; the trapezoid's two sides are the parallel ones:

Irregular shape? Split it into these pieces, compute each, and add. That decomposition trick is how surveyors and estimators handle any footprint.

rectangle = length × width
triangle = base × height ÷ 2
circle = π × r²; trapezoid = (a + b) ÷ 2 × h

Worked examples

Example 1: triangular garden bed

A corner bed with a 10 ft base and 6 ft height — how much mulch area?

  1. Measure the base and the perpendicular height to the far corner.
    base 10 ft, height 6 ft
  2. A triangle is half its surrounding rectangle.
    10 × 6 ÷ 2 = 30 sq ft

30 sq ft of bed to cover.

Example 2: round patio

A circular patio 12 ft across.

  1. Radius is half the diameter.
    r = 6 ft
  2. Apply π r².
    π × 6² = 113.1 sq ft

About 113 sq ft.

Example 3: trapezoid lot section

A lot section with parallel sides 80 ft and 60 ft, 50 ft apart.

  1. Average the parallel sides.
    (80 + 60) ÷ 2 = 70 ft
  2. Multiply by the distance between them.
    70 × 50 = 3,500 sq ft

3,500 sq ft (about 0.08 acres).

FAQ

Which "height" do I measure for a triangle?+

The perpendicular height: from the base straight up to the opposite vertex, meeting the base at 90°. The slanted side only equals the height in a right triangle where that side is vertical.

How is this different from the square footage calculator?+

Same math, different job: this page is unit-agnostic geometry for any shape; the square footage page is feet-only and remodel-focused (price per sq ft, yards, acres). That split keeps each page targeted.

How do I find the area of an irregular shape?+

Decompose it: split the outline into rectangles, triangles and trapezoids, calculate each and sum. For a curved pond-like outline, overlay a grid and count squares for a close estimate.

What about a parallelogram or an ellipse?+

Parallelogram = base × height (the rectangle formula with perpendicular height). Ellipse = π × a × b with the two half-axes. Both are planned as dedicated inputs.

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