While tables provide an effective way to display exact numbers or specific characteristics, graphs and charts can help you effectively generalize information, illustrate trends or patterns, and help your readers interpolate or extrapolate.

You have several different choices for graphs and charts; each has its own strengths. The primary types are:

• Simple bar graphs (one bar at each value) display approximate values
• Complex bar graphs (multiple bars at each value) compare data
  • Pictoral graphs replace the solid bars with icons to not only display the data, but illustrate the concept
• Pie charts illustrate proportions or percentages
• Line graphs show trends
• Stacked or area graphs demonstrate how components contribute to a total picture

General Guidelines

• Center the graph title at the top, making sure the title letters are larger than any other text on the graph.

• In general start each axis at zero; if the graph is too large, indicate a break in the grid (one standard exception are dates - if the x or y axis values are dates, you don't typically include the year 0 on the graph).

• Label each axis clearly, and include units.

• Avoid using two vertical (y) axes.

• Use either grid rulings or tick marks on the axis to mark the graph divisions.

• Use color, shading, or pattern to differentiate different sections of the graphs (lines, pieces of the pie, bars)

Guidelines for Bar Graphs

• Each bar should be the same width.
• The space between bars should be 1/2 the bar width (slightly more when using multiple bars).
• The Y-axis should be at least 1.75 times the X-axis.
• The longest bar should extend almost to the end of its axis (horizontal or vertical).
• Add exact numbers at the end of each bar for precision if appropriate.
• Include a key to delineate different parts of complex graphs.

Guidelines for Pie Charts

• Start at 12 o'clock, and go clockwise with the largest piece of the pie first.
• Make sure the whole pie adds up to 100%.
• Each wedges should be at least 5% (18 degrees); combine smaller wedges into Other.
• Include no more than 8 wedges
• Shade or color different wedges
• Include labels and exact percentages either inside the wedge, where possible, or immediately outside the circle

Guidelines for Line Graphs

• Put the dependent variable on the vertical (y) axis and the independent variable on the horizontal (x) axis
• At most, put 3-4 lines on a graph
• Use color or pattern to distinguish different lines
• Mark individual data points if appropriate
• Make the x & y axes proportional

Learn more about illustrations -->