Area Calculator
Calculate the area of squares, circles, triangles and eight more shapes.
All calculations happen locally in your browser — nothing is uploaded, stored or tracked.
Pick a shape
Ten common shapes to choose from.
Enter the dimensions
The fields update to match the shape.
Read the area
With perimeter where it makes sense.
What Is an Area Calculator?
An area calculator finds the two-dimensional size of a shape — how much surface it covers, measured in square units. It is used for flooring and tiling estimates, land measurement, painting, material planning and geometry homework.
Ten shapes are covered: square, rectangle, triangle, circle, parallelogram, trapezoid, ellipse, sector, regular hexagon and annulus (ring). Each shape shows the relevant dimensions, and most also report the perimeter.
Key Formulas
The annulus (ring) area is the difference between the outer and inner circle areas: π(R² − r²). The sector area is (θ ÷ 360) × πr² with the angle in degrees.
Your data never leaves your device.
Every calculation on this site runs in your browser using vanilla JavaScript. Nothing is uploaded, stored or tracked.
- 100% local, client-side calculations
- No data stored on any server
- No tracking, no analytics, no ads scripts
- Works offline once loaded
Frequently Asked Questions
How do I find the area of a circle?
Square the radius and multiply by π (≈3.14159). A circle with radius 5 has area 25π ≈ 78.54 square units.
How do I calculate the area of a triangle?
Multiply the base by the height and divide by 2.
What units does the calculator use?
Whatever units you enter — if you use metres, the area is in square metres; feet give square feet.
How do I calculate square footage for flooring?
Measure the room as a rectangle (length × width) or split it into rectangles and add the areas. The rectangle mode does this in one step.
What is the difference between area and perimeter?
Area is the surface covered (square units); perimeter is the distance around the edge (linear units). This calculator shows both.