The data-ink ratio is a term and design principle coined by Edward Tufte. Tufte refers to the amount of ink required to print points that represent relevant and meaningful data in a graphical display. Data ink in itself is the visual information, the core that represents the data, and that cannot be erased without loss of meaning.

Tufte defined the data-ink ratio as data-ink / total ink used by the graphic = 1 – proportion of a graphic that can be erased without loss of data.

In dashboard design the data-ink ratio refers to the pixel density of data represented versus non-essential pixels. The amount of redundant pixels should be kept to a minimum.

Five examples of non-data pixels in dashboard design and how they can be altered to
achieve a better data-ink ratio.:

  1. Diagrams and bar graphs that use color codes that bear no meaning should be simplified. For example all bar graphs could use the same color.
  2. Using 3D effects to render real-world objects should be reduced to work in 2D and without gloss
  3. Using real-world objects to represent data (such as gauges, dials, cockpits, etc.) should use simple graphical visual representations instead
  4. Using boarders around individual displays that are related should be avoided so that relationship between data sets is clear
  5. Using strong competing colors in dashboard areas that contain secondary or tertiary information should be avoided and instead muted.