A graph scale, or simply scale, refers to a set of numbers that indicate certain intervals on a graph used for measurement. There are many different types of graphs, including bar graphs, histograms, line graphs, and many more. Scales can present differently based on the types of graphs involved.
In general, the scale of the graph can differ between axes, but within an axis, such as on the x-axis of the coordinate plane, each interval represents the same value. Most typically, each mark on the x- and y-axes of the coordinate plane represents 1 unit, as shown in the figure below.
It is also possible to have different scales on each axis. For example, each interval on the y-axis could represent 2, or even 10 units, while each interval on the x-axis represents 1 unit. As long as the intervals have consistent magnitudes within each axis (i.e. the interval is 1 throughout the entire x-axis for a given graph), the scale of each axis can be very different.
If for example, we graphed a point on the coordinate plane at (1, 1), but each mark on the y-axis represented 1000 units while each mark on the x-axis represented 1 unit, we would not really be able to see the point we graphed since the scale of the y-axis is far too large. On the other hand, if we were trying to graph the point (1, 1000), but used a scale such that each interval on the y-axis was 1 unit, the graph would have to extend very far along the y-axis, which is not practical. Instead, we could scale the axes such that the x-axis has intervals of 1 unit, while the y-axis has intervals of 1000 units (or even 500, 200, etc.). As long as the interval is sufficiently large, we would still be able to fit the graph within a reasonable area of the page we are working on.
A coordinate plane is only one example of graph scales; there are numerous others. However, the same principles can be carried through many different types of graphs. Below is an example of a line graph in which the x-axis and y-axis have different intervals that are specifically chosen to ensure that the data presented is clear.
Although most basic graphs use a linear scale, it is worth noting that there are also different types of scales, such as logarithmic scales. A logarithmic scale is one in which each interval represents the subsequent power of 10. On a logarithmic scale, the numbers 10 and 100, and 30 and 300 are equally spaced (in a linear scale, 10 and 20, and 30 and 60, would be equally spaced). Logarithmic scales are useful when trying to concisely display data over a range of values in which the largest value is much larger than the smallest.
Because there are so many ways to present data, it is important to understand what type of graph(s) to use, as well as what scale to use, in order to most effectively present the data.