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Circle sector area calculator

Compute the area and arc length of a circle sector from its radius and angle.

Related tools

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Circle calculatorCompute the area, circumference and diameter of a circle from its radius.Annulus (ring) area calculatorCompute the area of a ring from its outer and inner radius.Area calculatorCompute the area of a rectangle, square, circle or triangle.Cone surface area calculatorCompute the total surface area and slant height of a cone from its radius 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.Regular polygon area calculatorCompute the area of a regular polygon from its number of sides and side length.Ellipse area calculatorCompute the area of an ellipse from its semi-major and semi-minor axes.

The Circle sector area calculator turns Radius, Angle (degrees) into Sector area, Arc length, instantly and for free. For instance, with Radius = 5 and Angle (degrees) = 90 it returns Sector area = 19.635 and Arc length = 7.854.

How to use it

  1. Enter your values: Radius, Angle (degrees).
  2. Read the result instantly: Sector area, Arc length.

Frequently asked questions

How does the Circle sector area calculator work?

It takes Radius and Angle (degrees) and derives Sector area and Arc length from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Radius and Angle (degrees). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Radius = 5 and Angle (degrees) = 90, the calculator returns Sector area = 19.635 and Arc length = 7.854. 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 Radius = 10 and Angle (degrees) = 180 instead, Sector area goes from 19.635 to 157.08 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Radius = 3 and Angle (degrees) = 45, Sector area comes out at 3.534. 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 Circle sector area calculator and the Circle calculator?

This one returns Sector area and Arc length; the Circle calculator returns Area and Circumference. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Annulus (ring) area calculator is the closest one after this: Compute the area of a ring from its outer and inner radius.

What else is worth having open alongside it?

Area calculator and Cone surface area calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
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 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.ExplainerThe Flat Pattern of a Cone Is a Sector, Not a CircleRoll a 50 mm cone 80 mm tall and its pattern is a 190.8° slice of a 94 mm circle. Flatten a nearly cylindrical lampshade and the pattern radius runs to 839 mm — the shallower the taper, the further away the apex.How-toHow to Find the Area of a Triangle: Base × Height and Heron's FormulaTwo reliable ways to find a triangle's area: half base times height when you know the height, and Heron's formula when you only know the three sides.