# Square Footage Calculator > Free square footage calculator: add rooms, yards and odd shapes, then convert square feet to acres, square yards and square metres. Formulas and examples. Canonical: https://brickbyclick.ai/square-footage-calculator Last updated: 2026-10-28 ## Area calculator for rooms, yards and lots Add one line for each part of the space. Split odd shapes into rectangles, triangles and circles, then add them up. ## Square feet to acreage conversion calculator Type in any box and the others update. One acre is exactly 43,560 sq ft. acres = square feet ÷ 43,560 square feet = acres × 43,560 *Square feet to acres* | Square feet | Acres | Square metres | | --- | --- | --- | | 1,000 sq ft | 0.0230 | 92.9 | | 2,000 sq ft | 0.0459 | 185.8 | | 5,000 sq ft | 0.1148 | 464.5 | | 7,500 sq ft | 0.1722 | 696.8 | | 10,000 sq ft | 0.2296 | 929.0 | | 15,000 sq ft | 0.3444 | 1,393.5 | | 20,000 sq ft | 0.4591 | 1,858.1 | | 21,780 sq ft | 0.5000 | 2,023.4 | | 43,560 sq ft | 1.0000 | 4,046.9 | | 87,120 sq ft | 2.0000 | 8,093.7 | | 100,000 sq ft | 2.2957 | 9,290.3 | | 217,800 sq ft | 5.0000 | 20,234.3 | *Acres to square feet* | Acres | Square feet | Square metres | | --- | --- | --- | | 0.1 acres | 4,356 | 405 | | 0.25 acres | 10,890 | 1,012 | | 0.5 acres | 21,780 | 2,023 | | 0.75 acres | 32,670 | 3,035 | | 1 acre | 43,560 | 4,047 | | 2 acres | 87,120 | 8,094 | | 5 acres | 217,800 | 20,234 | | 10 acres | 435,600 | 40,469 | ## How to calculate square footage Measure in feet and multiply. For other shapes, use the matching formula: rectangle = length × width triangle = base × height ÷ 2 circle = π × (diameter ÷ 2)² trapezoid = (side a + side b) ÷ 2 × height If you measured in inches, divide square inches by 144. In yards, multiply square yards by 9. In metres, multiply square metres by 10.7639. ### Worked example: a room and a lot 1. A 12 ft × 15 ft room: 12 × 15 = **180 sq ft**, or 20 sq yd (180 ÷ 9). 2. With 10% extra for flooring cuts: 180 × 1.10 = 198 sq ft to order. 3. A 100 ft × 150 ft lot: 100 × 150 = 15,000 sq ft; 15,000 ÷ 43,560 = **0.344 acres**. The calculator opens with the room and the converter with the lot, so you can check both. ### Odd-shaped rooms and yards Draw the space and cut it into simple shapes. An L-shaped room is two rectangles. A bay window is a rectangle plus a trapezoid. A curved bed is close to half a circle, so add a circle line and halve it, or enter the diameter of a circle of the same area. Add each piece as its own line. ## Square footage for flooring, painting and landscaping quotes - **Flooring and tile:** measure the floor wall to wall, add extra for cuts, and divide by the coverage on each box. - **Painting:** wall area is the room’s perimeter times the wall height, less large doors and windows. Divide by the coverage on the paint can and multiply by the number of coats. - **Sod, seed and mulch:** measure the lawn or beds in square feet. For mulch or soil, multiply by depth in feet for cubic feet, and divide by 27 for cubic yards. - **Cleaning and pressure washing:** many companies quote by the square foot, so a quick total helps you price on the first call. ## From measurement to a quote Multiply the area by your rate, then check the margin with the [margin calculator](https://brickbyclick.ai/margin-calculator). Bill the job with the [free invoice generator](https://brickbyclick.ai/free-invoice-generator), or email invoices with a card payment link through [BrickByClick Free](https://brickbyclick.ai/free-invoicing) for $0 a month. [Starter, $99 a month](https://brickbyclick.ai/starter-plan), adds estimates customers accept online, a job tracker and a calendar. ## Sources - 1 acre = 43,560 sq ft (10 square chains); 1 ft = 0.3048 m exactly, so 1 sq ft = 0.09290304 m²; 1 acre = 4,046.8564224 m²: [NIST Handbook 44, Appendix C (General Tables of Units of Measurement)](https://www.nist.gov/pml/owm/publications/nist-handbooks/handbook-44). Since 2023 the US uses the international foot for these conversions ([NIST, U.S. survey foot](https://www.nist.gov/pml/us-surveyfoot)). - Area formulas for rectangles, triangles, circles and trapezoids are standard geometry. ## Questions people ask ### How do I calculate square footage? Measure the length and width in feet and multiply them. A 12 ft by 15 ft room is 180 sq ft. For an odd shape, split it into rectangles and other simple shapes, work out each one and add them. ### How many square feet are in an acre? Exactly 43,560 square feet. That is the area of a strip 66 ft (one chain) wide and 660 ft (one furlong) long. ### How do I convert square feet to acres? Divide the square feet by 43,560. A 15,000 sq ft lot is 15,000 ÷ 43,560 = 0.344 acres, a little over a third of an acre. ### How many square feet is half an acre? 21,780 square feet. A quarter acre is 10,890 sq ft and a tenth of an acre is 4,356 sq ft. ### How do I convert square feet to square yards? Divide by 9, because a square yard is 3 ft by 3 ft. 180 sq ft is 20 sq yd. ### How do I convert square feet to square metres? Multiply by 0.0929. One square metre is about 10.764 sq ft, so 180 sq ft is about 16.7 m². ### How do I find the square footage of an irregular room? Sketch it and divide it into rectangles, triangles and part-circles. Measure each piece, add one line per piece in the calculator, and it adds them up. ### How much extra flooring should I buy? Many installers add a margin for cuts and breakage, more for diagonal layouts and small tiles. Check the flooring maker’s instructions, then enter that percentage as waste. ### How do I calculate the square footage of walls for painting? Multiply the room’s perimeter by the wall height, then subtract large doors and windows. A 12 by 15 ft room with 8 ft walls has 2 × (12 + 15) × 8 = 432 sq ft of wall before openings. ### How many square feet is a hectare? About 107,639 sq ft. 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