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Area calculator

Compute the area of a rectangle, square, circle or triangle.

Related tools

All Geometry tools →
Annulus (ring) area calculatorCompute the area of a ring from its outer and inner radius.Circle sector area calculatorCompute the area and arc length of a circle sector from its radius and angle.Cone surface area calculatorCompute the total surface area and slant height of a cone from its radius and height.Parallelogram area calculatorCompute the area of a parallelogram from its base and height.Triangle area calculatorArea of a triangle from base and height, three sides, or two sides and the angle between them.Trapezoid area calculatorCompute the area of a trapezoid from its two parallel sides and height.Hexagon area calculatorCompute the area of a regular hexagon from its side length.Pentagon area calculatorCompute the area of a regular pentagon from its side length.

Need Area? The Area calculator derives it from Shape, Dimension 1 (width / radius / base), Dimension 2 (height / length) in one step. For instance, with Shape = Rectangle, Dimension 1 (width / radius / base) = 4 and Dimension 2 (height / length) = 3 it returns Area = 12.

How to use it

  1. Enter your values: Shape, Dimension 1 (width / radius / base), Dimension 2 (height / length).
  2. Read the result instantly: Area.

Frequently asked questions

How does the Area calculator work?

It takes Shape, Dimension 1 (width / radius / base) and Dimension 2 (height / length) and derives Area from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

3 values: Shape, Dimension 1 (width / radius / base) and Dimension 2 (height / length). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Shape = Rectangle, Dimension 1 (width / radius / base) = 4 and Dimension 2 (height / length) = 3, the calculator returns Area = 12. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Shape = Square, Dimension 1 (width / radius / base) = 8 and Dimension 2 (height / length) = 6 instead, Area goes from 12 to 64 — which is why it is worth testing a few scenarios rather than trusting a single figure.

Which “Shape” option should I choose?

You can pick between « Rectangle », « Square », « Circle » and « Triangle ». Each one changes what the calculator works out, so switch and compare — the default is « Rectangle ».

What does it give for smaller values?

Scaled down to Shape = Rectangle, Dimension 1 (width / radius / base) = 2 and Dimension 2 (height / length) = 2, Area comes out at 4. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Homework and site work alike: how much paint a wall takes, how much water a tank holds, whether a corner is square — and, on the coordinate side, the slope between two points, the distance across a plan, the midpoint of a span.

What is the most common mistake?

Mixing units inside one shape. Entering a length in centimetres and a width in metres gives an area wrong by a factor of a hundred, and the result looks perfectly plausible.

What is the difference between the Area calculator and the Annulus (ring) area calculator?

Both return Area. What differs is what they ask for: this one wants Shape and Dimension 1 (width / radius / base), the Annulus (ring) area calculator wants Outer radius and Inner radius. Use whichever matches the numbers you already have.

Is there a tool for the next step?

Circle sector area calculator is the closest one after this: Compute the area and arc length of a circle sector from its radius and angle.

Further reading

All guides →
How-toHow to Calculate the Square Metres of a RoomFind a room's area by multiplying length by width. Here's the method for rectangular, L-shaped and round rooms, and why area drives your material orders.How-toCircle: Circumference and AreaCircumference is 2πr, area is πr². Here's how radius, diameter and π fit together, both formulas worked through, and how not to mix them up.ExplainerThe Pythagorean Theorem ExplainedIn a right triangle, a² + b² = c². Here's what the formula means, a worked example, how to find any side, and where it's used in real life.How-toHow to Calculate VolumeVolume is the space inside a shape. Here's how to find it for boxes, cylinders and spheres, and why keeping your units consistent is the whole game.How-toHow Many Tiles Do You Need? (Floor and Wall)Estimate tiles from the area to cover and one tile's size, then add for cuts and waste. Here's the method, with an example and the 10% rule.How-toWhat Size Air Conditioner Do I Need?Around 20 BTU per square foot is the starting rule. Here's how to size a unit from your room's area, adjust for sun and use, and why bigger isn't better.