Area Calculator

Use this free online area calculator to find the area of squares, rectangles, circles, triangles, and trapezoids. Simply pick your shape, enter its dimensions, and get an accurate area calculation instantly.

How to Use the Area Calculator

  1. Select your "Shape" - square, rectangle, circle, triangle, or trapezoid.
  2. Enter the required dimensions for that shape (e.g. Side for a square, Length and Width for a rectangle, Radius for a circle, Base and Height for a triangle, or Base 1, Base 2, and Height for a trapezoid).
  3. Click "Calculate" to compute the area.
  4. Review the "Area" result shown below the button.

Area Formulas Used for Each Shape

Area measures how much flat surface a shape covers. The calculator applies the standard textbook formula for the shape you pick and rounds the answer to three decimal places.

ShapeFormulaExample
Squareside × sideside 4 → 16
Rectanglelength × width12 × 10 → 120
Circleπ × radius × radiusradius 5 → 78.54
Triangle½ × base × heightbase 8, height 5 → 20
Trapezoid½ × (base 1 + base 2) × heightbases 20 and 14, height 9 → 153

For triangles and trapezoids, "height" means the perpendicular distance between the base and the opposite vertex or parallel side. It is not the length of a slanted side. Using a sloping edge instead of the true height gives an area that is too large.

Worked Example: Floor Area of an L-Shaped Room

Most real floors and plots are not a single neat shape, so split them into pieces the calculator can handle. Suppose a room is a 12 ft × 10 ft rectangle with a 6 ft × 4 ft alcove attached to one side. Calculate each part separately: 12 × 10 = 120 sq ft and 6 × 4 = 24 sq ft. Add them to get 144 sq ft. If a part needs to be cut out instead, such as a pillar or a built-in cupboard, subtract its area rather than adding it.

For a round table top with a 5 ft radius, the calculator returns π × 5 × 5 = 78.54 sq ft. If you only know the diameter, halve it first: a 10 ft diameter means a 5 ft radius.

Units and Common Area Conversions

The calculator has no unit selector. The answer is in the square of whatever unit you typed: metres give square metres, feet give square feet. Keep every dimension in the same unit. Mixing feet and inches, for example, produces a meaningless result, so convert 10 ft 6 in to 10.5 ft before entering it.

UnitEquals
1 square metre10.764 square feet
1 square foot0.0929 square metre, or 144 square inches
1 square yard (gaj)9 square feet
1 acre43,560 square feet, about 4,047 square metres
1 hectare10,000 square metres, about 2.471 acres

Local land units such as bigha, guntha and cent vary from state to state. Check the value used by your state's land records department before converting a plot measurement.

Practical Tips

  • When buying tiles, paint or flooring, add 5–10% to the computed area to cover cutting waste and breakage.
  • Doubling every side of a shape multiplies its area by four, not two. Keep this in mind when comparing plot or room sizes.
  • Property listings may quote carpet area, built-up area or super built-up area. A tape-measured floor gives you something close to carpet area, which is usually the smallest of the three.

Frequently Asked Questions

Square uses side², rectangle uses length × width, circle uses π × radius², triangle uses 0.5 × base × height, and trapezoid uses 0.5 × (base1 + base2) × height.

For base1 = 6, base2 = 4, and height = 3, the area is 0.5 × (6 + 4) × 3 = 15 square units.

The result is in square units of whatever you entered. Enter metres and you get square metres; enter feet and you get square feet. All dimensions for one shape must use the same unit.

This calculator needs the base and perpendicular height. With three sides a, b and c, use Heron's formula instead: work out s = (a + b + c) ÷ 2, then area = √(s × (s − a) × (s − b) × (s − c)). For sides 5, 6 and 7, s = 9 and the area is √216 ≈ 14.697.

Divide it into rectangles, triangles and trapezoids, find the area of each piece with this calculator, and add the results. Subtract the area of any cut-out such as a pillar or shaft. For land with curved or very uneven boundaries, a survey drawing is more reliable.
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