# Bar charts - constructing a bar chart

In the example, a pipe has been sealed in four different ways, and the amount of water leaking out in the same time has been measured.

Sealant method | Leakage (ml) |
---|---|

Parcel tape | 200 |

Glue gun | 210 |

Insulation tape | 10 |

Plumber's tape | 25 |

## Step 1 - axes

Draw two axes, x and y, and write the categories along the x axis.

Try to space them out evenly.

If the labels are too long, you could turn them on their side!

## Step 2 - scales

Draw a scale for the y axis. You need to take into account the biggest value in the table and the space available.

Write numbers on the y axis, making sure they are on the graph paper **lines** rather than in the spaces. Our highest number is 210, so this scale goes to 250. Each thin line is worth 10.

## Step 3 - draw the bars

Using a ruler, draw each bar. Find the value on the vertical scale so you know how high the bar must be drawn. Each bar should be the same width. You can colour them in so they are easier to see.

In this chart 25 on the scale is half way between 20 and 30.

## Step 4 - label your chart

Add a label to the y axis so it is clear what the numbers mean. You should include the unit the number was measured in - for this chart the unit is ml.

Finally, write a title for the chart that says what it is about.

Can you interpret a bar chart?