CanvasRenderingContext2D.arc

The CanvasRenderingContext2D.arc() method of the Canvas 2D API adds a circular arc to the current sub-path.

Syntax

void ctx.arc(x, y, radius, startAngle, endAngle [, anticlockwise]);

The arc() method creates a circular arc centered at (x, y) with a radius ofradius. The path starts at startAngle and ends at endAngle, and travels in the direction given by anticlockwise (defaulting to clockwise).

Parameters

x

The x-axis (horizontal) coordinate of the arc's center.

y

The y-axis (vertical) coordinate of the arc's center.

radius

The arc's radius. Must be non-negative.

startAngle

The angle at which the arc starts, measured clockwise from the positive x-axis and expressed in radians.

endAngle

The angle at which the arc ends, measured clockwise from the positive x-axis and expressed in radians.

anticlockwise Optional

An optional Boolean which, if true, causes the arc to be drawn counter-clockwise between the start and end angles. The default value is false (clockwise).

Examples

Drawing a full circle

This example draws a complete circle using the arc() method.

HTML

<canvas id="canvas"></canvas>

JavaScript

The arc is given an x coordinate of 100, a y coordinate of 75, and a radius of 50. To make a full circle, the arc begins at an angle of 0 radians (0°), and ends at an angle of 2π radians (360°).

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');

ctx.beginPath();
ctx.arc(100, 75, 50, 0, 2 * Math.PI);
ctx.stroke();

Result

Different shapes demonstrated

This example draws various shapes to show what is possible when using arc().

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');

// Draw shapes
for (let i = 0; i <= 3; i++) {
  for (let j = 0; j <= 2; j++) {
    ctx.beginPath();
    let x             = 25 + j * 50;                 // x coordinate
    let y             = 25 + i * 50;                 // y coordinate
    let radius        = 20;                          // Arc radius
    let startAngle    = 0;                           // Starting point on circle
    let endAngle      = Math.PI + (Math.PI * j) / 2; // End point on circle
    let anticlockwise = i % 2 == 1;                  // Draw anticlockwise

    ctx.arc(x, y, radius, startAngle, endAngle, anticlockwise);

    if (i > 1) {
      ctx.fill();
    } else {
      ctx.stroke();
    }
  }
}

Result

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Gecko-specific notes

Starting with Gecko 2.0 (Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1):

• The anticlockwise parameter is optional.
• Specifying a negative radius now throws an IndexSizeError error ("Index or size is negative or greater than the allowed amount").

See also

• The interface defining this method: CanvasRenderingContext2D
• Use CanvasRenderingContext2D.ellipse() to draw an elliptical arc