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What This Calculator Does

Calculate square feet from dimensions and combine up to 10 added or subtracted areas. Each region can be a rectangle, circle or triangle and can use its own measurement unit. Results include square metres, square yards, square inches and acres, with an area-by-area formula breakdown.

When to Use It

Use it to estimate the flat area of rooms, floors, walls and other measured surfaces. Split an L-shaped footprint into non-overlapping shapes. For a rectangular wall, use its length and height as the two dimensions and subtract windows or doors separately. Curved surfaces, arbitrary boundaries and sloped-roof projection are not modeled.

Inputs Explained

  • Shape: Rectangle takes length and width; Circle takes diameter; Triangle takes a base and the perpendicular height to that base, not two arbitrary sides.
  • Operation: Add includes the region; Subtract removes a cutout. Do not subtract the same opening twice.
  • Units: Feet & inches, Decimal feet, Inches, Metres or Centimetres. Dimensions within a region share a unit; separate regions may use different units.
  • Feet & inches: Feet must be non-negative whole numbers. Inches may be decimal, from 0 to less than 12. The combined dimension must exceed zero. Blank inches count as zero, but blank feet do not.

Use ordinary decimals with a decimal point or comma and no thousands separators. For example, 1,200 is interpreted as 1.2, not twelve hundred. Fractions, scientific notation and text with unit suffixes are not accepted; enter half an inch as 0.5.

Adding a region creates blank dimensions to complete before calculation. Editing, removing, or changing a shape or unit clears the old result. Reset restores one empty rectangle in Add mode using feet and inches. Inputs remain in component state and are not saved to URLs or browser storage.

How the Calculation Works

Normalize dimensions to feet:

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よくある質問

How do I calculate square feet?

For a rectangle, multiply length in feet by width in feet. A 12 ft by 10 ft room has 120 square feet. Circles use diameter; triangles use base and perpendicular height.

Is 12 feet 6 inches the same as 12.6 feet?

No. Six inches is half a foot, so 12 feet 6 inches equals 12.5 feet. Use the separate feet and inches fields to avoid decimal-foot mistakes.

How do I measure an L-shaped room?

Add non-overlapping rectangles, or calculate an outer rectangle and subtract the missing section. Use one approach consistently to avoid counting overlaps or subtracting twice.

What happens when I switch units?

Valid dimensions are converted to preserve physical size, subject to floating-point rounding. Invalid or blank dimensions are cleared and their inches fields reset to zero. Complete them before calculating again.

Does the result include flooring waste or certified living area?

No. It is geometric net area without material allowance, purchase rounding or jurisdiction-specific building and appraisal measurement rules.

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平方フィート計算機

部屋や床、複数の区域の面積を平方フィートで計算。

寸法を入力

区域1
ft
in
ft
in
A = L × W
最大10区域

桁区切りなしの小数を使用します。単位変更で有効な寸法を換算し、無効な値は消去します。空欄のインチは0です。

合計面積(平方フィート)

寸法を入力して面積を計算してください。

重ならない区域を加え、切り欠きは一度だけ引いてください。