CanvasRenderingContext2D: arc() method

arc(x, y, radius, startAngle, endAngle)
arc(x, y, radius, startAngle, endAngle, counterclockwise)

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

x

The horizontal coordinate of the arc's center.

y

The vertical coordinate of the arc's center.

radius

The arc's radius. Must be positive.

startAngle

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

endAngle

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

counterclockwise Optional

An optional boolean value. If true, draws the arc counter-clockwise between the start and end angles. The default is false (clockwise).

None (undefined).

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

HTML

<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.querySelector("canvas");
const ctx = canvas.getContext("2d");

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

Result

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

<canvas width="150" height="200"></canvas>

const canvas = document.querySelector("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 counterclockwise = i % 2 === 1; // Draw counterclockwise

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

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

Result

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