Area Calculator: Find the Area of 9 Shapes Free and Privately
An area calculator finds the flat surface a shape covers from its measurements. Choose one of nine shapes above (rectangle, square, circle, triangle, trapezoid, parallelogram, ellipse, rhombus or sector), pick the unit your measurements are in, and type the dimensions. The area appears as you type, with the formula used and the same area in ten units, including m², ft², hectares and acres.
Everything is calculated in your browser, so nothing you type is uploaded; you can check the Network tab in DevTools. The calculator gives areas in square units only. For three-dimensional shapes use the Volume Calculator, and to change a single length use the Length Converter.
Area Calculator Table of Use: Shapes, Formulas and Examples
| Shape and typical use | You enter | Formula | Example result |
|---|---|---|---|
| Rectangle: rooms, floors, plots | Length, Width | length × width | 12 ft × 10 ft = 120 ft² (11.1484 m²) |
| Square: tiles, patios | Side | side² | 4.5 m side = 20.25 m² |
| Circle: ponds, round tables | Radius | π × r² | r = 5 m = 78.5398 m² |
| Triangle: gables, garden beds | Base, Height | ½ × base × height | 8 × 5 = 20 square units |
| Trapezoid: sloped plots, cross-sections | Parallel side a (top), Parallel side b (bottom), Height | ½ × (a + b) × height | 6, 10, height 4 = 32 square units |
| Parallelogram: skewed panels | Base, Height | base × height | 7 × 3 = 21 square units |
| Ellipse: oval rugs, tracks | Semi-major axis (a), Semi-minor axis (b) | π × a × b | a = 5, b = 3 = 47.1239 square units |
| Rhombus: diamond tiles, kites | Diagonal 1, Diagonal 2 | ½ × d₁ × d₂ | 10 and 6 = 30 square units |
| Sector: pie slices, fan-shaped beds | Radius, Angle in degrees | (θ ÷ 360) × π × r² | r = 10, 90° = 78.5398 square units |
Area Calculator Features
- Nine shapes: each has its own labelled inputs, and the Formula box shows the equation in use.
- Eight length units: millimetres, centimetres, metres, kilometres, inches, feet, yards and miles, all converted using exact definitions.
- Same area in other units: mm², cm², m², hectares, km², in², ft², yd², acres and mi², so a room measured in feet can be read in m².
- Decimal point or comma: both are accepted. A thousands separator such as “1,500” is refused with a message, because it could mean 1.5 or 1500.
- Input checks: negative values are rejected, a sector angle above 360 is rejected, and results too large or too small to calculate say so instead of showing a wrong number.
- Rounded for reading: results show up to four decimal places, or six significant digits below 1.
- Diagram and copy: a generic outline of the shape (not drawn to scale; only the sector follows your angle), and a Copy button that copies the shape and its area, such as “Rectangle area: 120 ft²”.
Limits: all dimensions share one unit, so convert mixed measurements first, and fractions such as 3 3/8 must be typed as decimals. The Fraction Calculator converts a fraction to a decimal for you.
How to Use the Area Calculator
- Under Select shape, press the shape that matches what you are measuring.
- Open Unit of the dimensions and choose the unit your tape measure used.
- Type each dimension into its field, for example Length (ft) and Width (ft). Every field must be filled for a result to show.
- Read the area in the Result panel, the equation under Formula, and the conversions under Same area in other units.
- Press Copy to copy the result, or change the shape to measure the next part of the space.
Who Can Use the Area Calculator
Homeowners can size flooring, paint, turf or tiles, and gardeners can work out a round or oval bed. Students can check geometry homework against the displayed formula. Builders, surveyors and buyers of land can read a plot in acres or hectares without a second tool.
Once you have the area, multiply by the price per unit, take off a sale with the Discount Calculator, then add tax with the VAT Calculator. Suppliers often add extra for offcuts, so ask yours for an allowance and apply it with the Percentage Calculator. If a price is quoted in another currency, the Currency Converter helps, and the Unit Converter and Scientific Calculator cover other conversions and quick checks.
Area Calculator FAQs
How do I calculate the area of a room in square feet?
Choose Rectangle, set "Unit of the dimensions" to Feet, then enter the room's length and width. A room of 12 ft by 10 ft gives 120 ft², and the "Same area in other units" list shows 11.1484 m². For an L-shaped room, work out each rectangle separately and add the results.
How do I convert square feet to square meters?
Multiply square feet by 0.09290304, because one foot is exactly 0.3048 m and 0.3048 squared is 0.09290304. So 100 ft² is 9.2903 m². In the calculator, pick Feet as the unit and read the m² row under "Same area in other units", which is calculated from the same exact definition.
How many square feet are in an acre?
One international acre is exactly 43,560 square feet, or 4,046.8564224 square metres. A hectare is 10,000 m², which is about 2.4711 acres. To check, choose Rectangle, set the unit to Feet, enter 43560 and 1, and the acres row shows 1, with 4,840 in the yd² row.
Do I enter the diameter or the radius for a circle?
The calculator asks for the radius, which is half the diameter. A round pond 10 m across has a radius of 5 m, so choose Circle, enter 5 and read 78.5398 m². Entering the diameter by mistake would make the area four times too large, because the radius is squared in the formula.
Which height do I use for a triangle, trapezoid or parallelogram?
Use the perpendicular height: the straight distance at a right angle from the base to the opposite corner or side. The length of a slanted side is longer than the height and would overstate the area. A triangle with base 8 and height 5 has an area of 20 square units.
How do I find the area of an L-shaped or irregular shape?
Split the shape into rectangles, triangles or other simple shapes, calculate each with the same unit, and add the areas. To remove a cut-out such as a hearth, calculate its area and subtract it. The calculator handles one shape at a time and does not combine shapes for you.
Are my measurements sent to a server?
No. The area calculator runs entirely in your browser. The numbers you type are not uploaded, saved or shared, and you can confirm this in the Network tab of your browser's DevTools. There is no sign-up, and closing the page clears everything you entered.