Start with the variable and unit
“Population” is not enough. A legend should distinguish total population from population density, and state whether density means people per square kilometer, square mile or another unit.
Map skills · interactive
A map legend turns marks into meaning
Color is not data. A circle is not a city until the map explains it. Build a legend and see how class breaks, units and symbols change the reading.
A complete legend states
- What variable the map represents
- Which unit and class breaks are used
- What points, lines and areas mean
- How missing or exceptional values appear
Legend laboratoryChange the visual system and watch the meaning change.
Elevation
m above sea level · 5 sequential classes
0 – 1,600Low ground
1,600 – 3,200
3,200 – 4,800Upland
4,800 – 6,400
6,400 – 8,000High mountain
City or observation
Major route or river
Selected area
Class breaks shape the pattern
The same values can look smooth, polarized or uniform depending on where the legend divides them. More classes reveal variation but increase cognitive load. Fewer classes read quickly but can hide important differences.
Use more than color
Point shape, line style, labels and patterns provide redundant meaning. That helps readers with color-vision differences and keeps the map understandable in print, on dim screens and at small sizes.
Legend FAQ
Small box. Large responsibility.
What is a legend on a map?
A map legend, also called a key, explains the meaning of colors, lines, areas, patterns and point symbols used on the map.
Does every map need a legend?
A legend is needed whenever the symbols or colors are not obvious from direct labels or familiar convention. Very simple maps may explain themselves without a separate key.
What should a good map legend include?
It should name the variable, show every relevant symbol or class, state units, explain class breaks and identify unusual or missing values.
Use the skill