About Area Calculator
This area calculator is free, needs no sign-up and runs in your browser, so your measurements are never uploaded. It covers eleven shapes: square, rectangle, triangle, circle, ellipse, trapezoid, parallelogram, rhombus, circle sector, regular polygon and annulus (a ring). Each shows its formula, the substitution step by step, and a labelled diagram.
The result is given in the square of the unit you measured in, and also converted to square metres, square feet, square yards, square kilometres, square miles, acres and hectares. For land in Bangladesh it adds decimal (shotangsho), katha and bigha, using the same factors as the unit converter on this site.
Where the dimensions also give a perimeter or circumference, that is shown too. Every number is calculated on your device.
How to use Area Calculator
- Choose the shape from the list.
- Type its dimensions, such as length and width or radius. The labels in each box name the measurement.
- Pick the unit you measured in, and the unit you want the area converted to.
- Read the area, the converted value and the table of every unit.
- Compare your shape with the labelled diagram to make sure each number is the right measurement.
- Open the step-by-step working to see the formula with your numbers in it.
Features
- Eleven shapes, each with formula, working and diagram.
- Eight length units for the inputs, from millimetres to miles.
- Result converted to square metres, feet, yards, kilometres, miles, acres and hectares.
- Bangladesh land units: decimal (shotangsho), katha and bigha.
- Perimeter or circumference where the inputs allow it.
- Regular polygon for any number of sides from 3 to 1000.
- Sector area from the angle in degrees, annulus from outer and inner radius.
- Clear errors, such as an inner radius larger than the outer one.
Area formulas
Every formula multiplies two lengths, so the area is in the square of the length unit: centimetres give square centimetres.
For a regular polygon the formula uses the number of sides n and the side s. For a sector, the fraction of the circle is the angle over 360 degrees.
Square: s²
Rectangle: l × w
Triangle: ½ b h
Circle: π r²
Ellipse: π a b
Trapezoid: ½ (a + b) h
Parallelogram: b h
Rhombus: ½ p q
Sector: (θ / 360°) π r²
Regular polygon: n s² / (4 tan(π / n))
Annulus: π (R² − r²)Worked examples
Circle with radius 5 m gives 78.5398 m²
π × 5² = π × 25. The circumference is 31.4159 m.
Trapezoid with parallel sides 5 and 9 and height 4 gives 28 square units
½ × (5 + 9) × 4 = 28.
Regular hexagon with side 4 gives 41.5692 square units
6 × 4² / (4 tan 30°).
Ring with outer radius 8 and inner radius 5 gives 122.5221 square units
π × (64 − 25) = 39π.
One square metre in other units
| Unit | Value of 1 m² |
|---|---|
| Square metres (m²) | 1 |
| Square feet (ft²) | 10.76391 |
| Square yards (yd²) | 1.19599 |
| Square kilometres (km²) | 0.000001 |
| Square miles (mi²) | 3.8610216e-7 |
| Acres | 0.00024710538 |
| Hectares (ha) | 0.0001 |
| Decimal / Shotangsho (BD) | 0.024710538 |
| Katha (BD) | 0.014949876 |
| Bigha (BD) | 0.00074749378 |
Good to know
Land units in Bangladesh
This calculator uses 1 decimal (shotangsho) = 435.6 square feet, 1 katha = 720 square feet and 1 bigha = 20 katha = 14,400 square feet. The katha and bigha are not the same everywhere in the country, and some districts use other values. Treat the converted figure as an estimate and check the deed or ask the local land office before you buy or sell.
Precision
Results are calculated in double-precision floating point and shown to six decimal places. The ellipse perimeter has no exact closed form, so it is shown as Ramanujan’s approximation, which is very accurate for any ellipse.
Privacy: how it works
- All calculations run in your browser tab. The measurements you enter are not sent to Ulkaa or to any other server, and there is nothing to sign in to.
Tips
- Measure everything in the same unit before you enter it, or set the unit selector to match.
- The height of a triangle, trapezoid or parallelogram is the perpendicular distance, not the slanted side.
- For an L-shaped room, split it into two rectangles, find each area and add them.
- A rhombus needs its two diagonals, not its side length.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Your measurements are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Your measurements are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
How do I calculate the area of a rectangle?
Multiply the length by the width. A rectangle 8 m by 5 m has an area of 40 m².
What is the area of a circle?
It is π times the radius squared. With a radius of 5 the area is π × 25, about 78.54 square units. If you know the diameter, halve it first.
How do I find the area of a trapezoid?
Add the two parallel sides, multiply by the height and halve the result: ½ (a + b) h.
How do I convert square feet to katha?
With 1 katha = 720 square feet, divide the area in square feet by 720. The calculator does this when you select katha as the output unit.
What is the area of a regular hexagon?
Use n s² / (4 tan(π/n)) with n = 6, which is about 2.598 s². Pick Regular polygon and enter 6 sides.
Why is my area in square units, not units?
Area counts unit squares, so centimetres become square centimetres. Convert with the squared factor, not the plain length factor; the output selector does this for you.
Popular Area Calculator pages
- Square Area CalculatorEnter the side of a square to get its area and perimeter.
- Rectangle Area CalculatorEnter the length and width of a rectangle to get its area and perimeter.
- Triangle Area CalculatorEnter the base and the perpendicular height of a triangle.
- Circle Area CalculatorEnter the radius of a circle to get its area and circumference.
- Ellipse Area CalculatorEnter the two semi-axes of an ellipse.
- Trapezoid Area CalculatorEnter the two parallel sides and the height.
- Parallelogram Area CalculatorEnter the base and the perpendicular height.
- Rhombus Area CalculatorEnter the two diagonals of a rhombus.
- Sector Area CalculatorEnter the radius and the central angle of a sector.
- Regular Polygon Area CalculatorEnter the number of sides and the side length.
- Hexagon Area CalculatorEnter the side of a regular hexagon.
- Annulus Area CalculatorEnter the outer and inner radius of a ring.
- Land Area CalculatorEnter the sides of a plot and read its area in katha, decimal, bigha, acres and square feet.