Area Calculator
Work out the exact area of a square, rectangle, circle, triangle, trapezoid, parallelogram or ellipse. Pick a shape, enter your measurements, and get the answer in the unit you need.
Please enter valid, positive numbers in every field.
How to calculate the area of any shape
Area tells you how much flat space a shape covers, and it’s the number behind most practical measuring jobs: how much laminate to order for a floor, how many litres of paint a wall needs, or how big a plot of land actually is. The calculator above handles the seven shapes people measure most often, but the maths behind each one is simple enough to do by hand once you know the formula.
Area formulas for common shapes
Rectangle
A rectangle’s area is its length multiplied by its width. This is the formula most people reach for first, since floors, rooms, gardens and screens are usually treated as rectangles even when they’re not perfectly regular.
Square
A square is a rectangle with four equal sides, so you only need one measurement.
Circle
A circle’s area depends on its radius (the distance from the centre to the edge) and the constant pi, which is roughly 3.14159.
If you only have the diameter, halve it first to get the radius before applying the formula.
Triangle
For a triangle, you need the length of one side (the base) and the height measured at a right angle from that base to the opposite point.
Trapezoid
A trapezoid has two parallel sides of different lengths. Add those two lengths together, multiply by the height between them, then halve the result.
Parallelogram
A parallelogram uses the same idea as a rectangle, but the height is measured perpendicular to the base rather than along the slanted side.
Ellipse
An ellipse is a stretched circle with two radii: the longest (semi-major axis) and shortest (semi-minor axis).
Converting between area units
Once you have an area, you’ll often need it in a different unit — a builder’s quote in square metres, a carpet supplier’s price per square foot, or a land listing in acres. Here are the conversions used most often in the UK:
| From | To | Multiply by |
|---|---|---|
| Square feet (ft²) | Square metres (m²) | 0.0929 |
| Square metres (m²) | Square feet (ft²) | 10.764 |
| Square inches (in²) | Square centimetres (cm²) | 6.4516 |
| Square yards (yd²) | Square metres (m²) | 0.8361 |
| Square metres (m²) | Acres | 0.000247 |
Where area calculations come in handy
- Flooring and tiling – measure the room as one or more rectangles to know how many square metres of flooring, tile or carpet to buy.
- Painting and decorating – wall area, minus doors and windows, tells you how many tins of paint or rolls of wallpaper a room needs.
- Gardening and landscaping – lawn, decking and flower bed area determines how much turf, gravel or soil to order.
- Land and property – irregular plots are often broken into rectangles and triangles, then added together for a total area.
- Construction – slab, roofing and insulation quantities are almost always priced per square metre or square foot.
Frequently asked questions
How do you calculate area?
Area is calculated using a formula specific to the shape you’re measuring. For a rectangle, multiply length by width. For a circle, multiply pi by the radius squared. For a triangle, multiply base by height and divide by two. The calculator above applies the correct formula automatically once you choose a shape.
What unit is area measured in?
Area is always expressed in square units — square metres (m²), square feet (ft²), square centimetres (cm²) and so on — because it describes a two-dimensional space rather than a single length. Land is sometimes measured in acres or hectares instead.
How do I convert square feet to square metres?
Multiply the area in square feet by 0.0929 to get square metres. To convert the other way, multiply square metres by 10.764 to get square feet.
Can I calculate the area of an irregular shape?
Yes — split the irregular shape into simpler shapes like rectangles and triangles, calculate each one separately, then add the results together for the total area.