Garden Bed Area Calculator
Find the area of common garden bed shapes for material planning.
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Calculating Garden Bed Area
Knowing the area of your garden bed helps you estimate soil, mulch, compost, fertilizer, and plant quantities. This calculator handles the most common bed shapes.
For irregular shapes, break them into rectangles and triangles, calculate each, and add them together.
Bed area calculations use the standard geometric formulas: rectangle = L × W, circle = π × r², triangle = 0.5 × base × height. For irregular beds, break the shape into rectangles and triangles, calculate each section, and sum them.
Practical use: area drives every quantity estimate — soil volume, mulch, seed coverage, fertilizer, weed fabric. Getting area right first saves money on over-ordering and frustration from under-ordering.
Keyhole beds (a path cut into a circular bed) are popular in permaculture — they maximize plantable area within arm's reach. A 6-foot diameter circle has an area of π × 3² ≈ 28 sq ft; subtracting the keyhole access path (about 2 sq ft) leaves ≈26 sq ft of growing space, all within 3 feet of the path edge.
For sloped ground, measure the horizontal footprint, not along the slope. A 10-foot bed on a 20° slope has a horizontal span of 10 × cos(20°) ≈ 9.4 feet. The calculator uses horizontal measurements since soil volume and plant spacing are based on horizontal area.
See also: Soil Volume Calculator · Mulch Calculator