---
name: Data-ink ratio
slug: data-ink-ratio
category: pattern
status: published
created: 2026-08-21T00:00:00.000Z
modified: 2026-08-21T00:00:00.000Z
definition: "Tufte's measure of chart economy: the share of ink that would be
  missed if erased, with everything else a candidate for deletion."
aliases:
  - name: data-ink
  - name: data to ink ratio
tags:
  - dataviz
  - perception
relations:
  contrastWith:
    - chartjunk
  variantOf: []
  partOf: []
  seeAlso:
    - chart
implementations: []
sources:
  - title: "Wikipedia: Data-ink ratio"
    url: https://en.wikipedia.org/wiki/Data-ink_ratio
demo: inline
exhibit: false
useWhen: deciding what a chart can lose before it loses meaning
---

Tufte defined data-ink as the non-erasable core of a graphic, the ink whose removal would
take a number with it, and the data-ink ratio as that quantity divided by the total ink the
[chart](/chart) spends. Two rules follow, and they are the whole method: maximise the
ratio, within reason, and then revise and edit. In practice you do it by erasure. Take a
finished chart, delete one thing, and ask what the reader lost. A plot fill, a box frame, a
legend for a single series, and every other gridline usually cost nothing. The line and the
dots cost everything.

The word sits next to its complement. The data-ink ratio measures how much of a chart's
ink carries data; [chartjunk](/chartjunk) names the ink that carries none. One is a number
you can watch move as you delete, the other is a name for what you are deleting, and
neither is much use without the other.

Treat the ratio as a heuristic, not a law, because it can be gamed and it can be pushed
past the point of use. It counts ink, not comprehension, so a chart can score well and
still be hard to read: erase the [axis](/axis) labels and the ratio improves while the
reader loses the scale, and strip the gridlines from a plot people are meant to read exact
values off and you have optimised the measure instead of the chart. Critics have made this
point since the 1980s, and controlled studies of "minimal" versus embellished charts have
repeatedly failed to show the clean advantage the rule implies. The defensible version is
narrower and still worth having: given two charts that answer the reader's question equally
well, prefer the one that spends less ink saying it.

The form Tufte pushed the idea furthest with is the [sparkline](/sparkline), a chart
reduced to almost nothing but its marks and set inline with the sentence it belongs to. It
has no axes, no gridlines, no legend and no frame, and it works because it is not being
asked for precision: the exact figure is printed beside it in the text, and the picture is
carrying only the shape of the trend. That is the honest reading of a high ratio. It is not
that decoration is immoral, it is that every mark should be answering something the reader
actually asked.