Area Calculator
Pick a shape, enter its dimensions in whatever unit you measured with, and this applies the standard formula for that shape — length times width for a rectangle, pi times the radius squared for a circle, the mean of the two parallel sides times the height for a trapezoid. The same area is then reported in square metres, square feet, square yards, square inches, acres and hectares, so a room measured in feet can be read off in square metres and a plot measured in metres can be read off in acres.
- Accurate
- Real-time
- Easy to use
- 100% free
Area
192.00 ft²
Square feet
192.00 ft²
Details
Updates as you typeThe three dimensions below are read differently for each shape. The working under the result names what each one was used as.
Switching this restates the dimensions rather than reinterpreting them, so the area stays the same size. It is reported in this unit squared and converted to six other units.
Rectangle: the length. Triangle or parallelogram: the base. Circle: the radius. Trapezoid: the first parallel side. Ellipse: the longer semi-axis.
Rectangle: the width. Triangle or parallelogram: the perpendicular height. Trapezoid: the second parallel side. Ellipse: the shorter semi-axis. A circle ignores it.
Only the trapezoid uses this: the perpendicular distance between its two parallel sides a and b. Every other shape ignores it.
Summary
Area
192.00 ft²
- Square metres
- 17.8374 m²
- Square feet
- 192.00 ft²
- Square yards
- 21.3333 yd²
- Square inches
- 27,648.00 in²
- Acres
- 0.004408 acres
- Hectares
- 0.001784 ha
- For a rectangle, a is the length, b is the width. Input h is ignored for this shape.
- Heights must be perpendicular. The height of a triangle or a parallelogram is the straight-line distance from the base to the opposite vertex or side, not the length of a slanted edge.
- 1 acre = 43,560 ft² = 4,046.8564224 m², and 1 hectare = 10,000 m² ≈ 2.4711 acres. Both follow from the international definition of the yard as exactly 0.9144 m.
- For an irregular room, split it into rectangles, work each one out separately and add the results together.
How this is calculated
- Shape
- Rectangle
- Length (a)
- 16.0000 ft
- Width (b)
- 12.0000 ft
- Area = a × b
- 192.00 ft²
- Square metres = ft² × 0.09290304
- 17.8374 m²
- Square feet = m² ÷ 0.09290304
- 192.00 ft²
- Acres = m² ÷ 4046.8564224
- 0.004408 acres
Compare scenarios
See how one change moves the result
- CurrentYour inputs as they stand192.00 ft²Current
- Dimension a — length, base, radius or semi-axisft 20240.00 ft²
- Dimension b — width, height or second sideft 15240.00 ft²
Frequently asked questions
How do I work out the square footage of a room?
Measure the length and the width in feet, choose "Rectangle or square" and "Feet", and enter them as a and b. The area is length times width — a room 16 ft by 12 ft is 192 square feet. For an L-shaped or otherwise irregular room, split it into rectangles on paper, run each rectangle through separately, and add the answers together.
Which boxes do I fill in for each shape?
Every input stays on screen whichever shape you pick, so the working under the result always names what each number was read as. Rectangle: a is the length and b the width. Triangle and parallelogram: a is the base and b the perpendicular height. Circle: a is the radius and nothing else is used. Trapezoid: a and b are the two parallel sides and h is the distance between them. Ellipse: a and b are the two semi-axes, which is to say half the long width and half the short width.
How many square feet are in an acre?
Exactly 43,560. An acre is defined as 4,840 square yards, and a yard is exactly 0.9144 metres, so an acre is 4,046.8564224 square metres and a square foot is 0.09290304 square metres — divide one by the other and 43,560 falls out with no rounding. A hectare is a round 10,000 square metres, which works out at about 2.4711 acres.
Is the height of a triangle the same as its slanted side?
No, and it is the most common mistake here. The height must be perpendicular to the base: the straight-line distance from the base to the opposite vertex, measured at a right angle. A slanted side is always longer than that perpendicular distance, so using it inflates the area. The same applies to a parallelogram, where the height is the gap between the two parallel sides rather than the length of the sloping edge.
Why does the area not change when I switch the unit?
Because the dimensions are restated rather than reinterpreted. A room that is 16 feet long is 4.8768 metres long, so switching the unit selector to metres rewrites 16 as 4.8768 and the physical area stays exactly the same — only the number and the label on the headline change. If you want to enter a genuinely different measurement, change the unit first and then type the new figures.
What is the formula for the area of an ellipse?
Pi times the two semi-axes multiplied together, or pi times a times b. A circle is the special case where the two semi-axes are equal, which collapses the formula to pi times the radius squared. So an oval 6 units across one way and 4 units across the other has semi-axes of 3 and 2, and an area of 6 pi, about 18.85 square units.