Getting Started With Charts

This page describes the basics of using the Chart API to make charts.

Google Chart Usage Policy

There's no limit to the number of calls per day you can make to the Google Chart API. However, we reserve the right to block any use that we regard as abusive.

Overview

Viewing Charts in This Documentation

All the chart images in this documentation are generated live, using the Chart API. To view the URL of any image, do the following:

  • If you are using Firefox, right-click and then select "View Image" or "Properties".
  • If you are using Internet Explorer, right-click and then select "Properties".

To make a URL easier to read, this document often shows it on multiple lines. When you are using the Google Chart API, you must supply a URL on a single line.

The Google Chart API returns a chart image in response to a URL GET or POST request. The API can generate many kinds of charts, from pie or line charts to QR codes and formulas. All the information about the chart that you want, such as chart data, size, colors, and labels, are part of the URL. (For POST requests, it's a little different, but don't worry about that now).

To make the simplest chart possible, all your URL needs to specify is the chart type, data, and size. You can type this URL directly in your browser, or point to it with an <img> tag in your web page. For example, follow this link for a pie chart:

https://chart.googleapis.com/chart?chs=250x100&chd=t:60,40&cht=p3&chl=Hello|World

 

The preceding link is an example of a basic Chart API URL. All Chart URLs have the following format:

https://chart.googleapis.com/chart?cht=<chart_type>&chd=<chart_data>&chs=<chart_size>&...additional_parameters...

All URLs start with https://chart.googleapis.com/chart? followed by the parameters that specify chart data and appearance. Parameters are name=value pairs, separated by an ampersand character (&), and parameters can be in any order, after the ?. All charts require at minimum the following parameters: cht (chart type), chd (data), and chs (chart size). However, there are many more parameters for additional options, and you can specify as many additional parameters as the chart supports.

Let's examine the URL above in more detail:

URL Components

Yellow pie chart

https://chart.googleapis.com/chart?
  cht=p3&
  chs=250x100&
  chd=t:60,40&
  chl=Hello|World
https://chart.googleapis.com/chart?
This is the base URL for all chart requests.
cht=p3
The chart type: here, a 3D pie chart.
chs=250x100
The chart size (width x height), in pixels. See the maximum values here.
chd=t:60,40
The chart data. This data is in simple text format, but there are other formats.
chl=Hello|World
The slice labels.
&
Parameters are separated by an ampersand. Note: When embedding an URL in HTML, for example as the src attribute of an <img> tag, you should replace the & between parameters with the characters &amp; This includes when you generate page HTML with PHP or some other language. However, when typing a URL in the browser, or when calling a URL in code, for example when fetching a URL in PHP or Perl, you should use the & mark.

Copy and paste this URL in your browser and try making a few changes: add additional values to the data (don't forget to add a comma before each new data value). Add new labels (put a | mark before each new value). Make the chart bigger.

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How To Make a Chart

Here's how to create an image chart:

  1. Decide on a chart type. See the gallery for a list of charts; chart type is specified by the cht parameter. Sketch out all the components that you want your chart to have (axes, labels, backgrounds, and so on), and if necessary, figure out pixel dimensions for the various components (total chart size, legend size, and so on). You should read the documentation carefully for your chart type first, or you might have a frustrating experience.
  2. Create and format your chart data. Data is specified using the chd parameter. You'll need to decide which format to use for your data:
    • Choose a data format. You can use simple text format for your chart data, which is easy to read, but takes more space to send, or use one of the encoding types, which is smaller to send, but restricts the range of values you can send.
    • Decide whether your data must be scaled to fit your chart. Different formats support different ranges of values. You might want to scale your data so that it spans the full range of values allowed by your format, to make differences more obvious. You can do this either by scaling your data to fit within the data format that you use, or you can use text formatting with custom scaling.
    • Encode your data, if necessary. If you've chosen an encoded format, we offer some JavaScript to help with other encoding types.
  3. Specify the chart size. Chart size is specified using the chs parameter. See the documentation for the format, and maximum values.
  4. Add additional parameters. Each chart's documentation lists the available optional parameters. Typical options include labels, titles, and colors. Note that all label or title text must be UTF-8 encoded. Note that many parameters allow you to enter multiple values. For example, the chm parameter lets you put a shape on a single data point on a chart. You can put shapes on multiple data points using the chm parameter, but to do this, you do not specify the chm parameter multiple times in your URL (for example, WRONG: chm=square&chm=circle&chm=triangle). Instead, parameters that take multiple values use a delimiter, such as a comma or vertical bar, between multiple values in the same parameter. For chm, it is a bar, so you'd have something like this: RIGHT: chm=square|circle|triangle. See the details of each parameter to learn how to specify multiple parameters.
  5. Build your URL string. The URL starts with https://chart.googleapis.com/chart? and is followed by all your required (cht, chd, chs) and optional parameters. Note: If you are using your URL in an <img> tag, you'll have to change all your & characters to &amp; in your link. Example: <img src="https://chart.googleapis.com/chart?chs=250x100&amp;chd=t:60,40&amp;cht=p3&amp;chl=Hello|World" />.
  6. Use GET or POST to get your image. GET, is either when you type the URL directly into your browser, or use it in an <img> tag. However, URLs are limited to 2K in length, so if you have more data than that, or have a taste for blood, you should consider using POST instead, as described here.
  7. Create clickable regions. You can optionally create an image map for the chart that will let you add hyperlinks or click elements to specific chart elements. See Creating a Chart Image Map for details.

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Glossary of Chart Terms

Here are a few important terms that we use in this documentation:

Series
A related set of data in a chart. What constitutes a series depends on the chart type: in a line chart, a series is a single line; in a pie chart, each entry is a slice, and all slices together are a series. In a bar chart, a series is all the bars from the same set of data; different series are either grouped side by side or stacked atop each other, depending on the bar chart type. The following chart demonstrates a grouped bar chart with two series, one in dark blue, one in light blue:
Bar chart showing two series: Cats and Dogs.
Axis labels
Numeric or text values along each axis. In the previous chart, it would be the labels "Jan," "Feb," "Mar," "0," "50," "100."

Chart Components

Here are some of the components of a chart:

Various regions of a chart.
Chart area
The area showing the series art. See "Chart Components" sidebar for more details.
Legend
A small area on the chart describing the series. In the chart above, it is the section that lists "Cats" and "Dogs".
Parameter
A key=value pair used in the URL. For example: chxt=x, where chxt is the parameter name and x is the parameter value.
GET and POST
Two methods of sending your Chart URL. GET is typically done either by typing a URL in the browser, or by making it the source of an <img> tag. POST requests are more complex to make, but can include much more data. The main reason to use POST instead of GET is that a POST request can take much more data than a GET request (16K characters vs 2K characters). POST is covered here.
Pipe character
The | character, often used as a parameter value delimiter—that is, a character to break up multiple values. Commas and ampersands (&) are also used as delimiters in the Chart URL.
Compound charts
A chart that is a combination of two different chart types: for example, a bar chart with a line, or a line chart with candlestick markers. See Compound Charts.

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Optimizations

Now that you've learned the basics of making a chart, here are a few optimizations that you can use.

Using POST

URLs are limited to 2K in length, so if your chart has more data than that, you'll have to use POST instead of GET, as described here. GET is when you type your chart URL into your browser URL bar, or use it as the source of an <img> element in a web page. POST requires additional programming in another language, such as PHP or PERL.

Making Charts in JavaScript

You can use the Google Visualization API to create image charts for you. The Google Visualization API is a JavaScript-based API that gives you tools to to create, filter, and manipulate data, or to query Google Spreadsheets or other sites for data. You can use the Visualization API to create your data, then have it call the Image Charts API to render the chart on the page. For more information, see the Generic Image Chart documentation, or look in the Visualization gallery for any Google charts marked (Image).