Examples · Box plot

Box plot examples

Two classes can share an average and still feel very different. In these fictional quiz scores, Periods 1 and 3 both average about 80, but Period 3 has the tighter box and one student far below the rest, at 38. Period 4 sits lower overall, and its 99 stands apart at the top.

When to use it

  • Compare medians and the spread of values across several groups at once
  • Spot outliers — the readings far from everyone else — before they skew an average

Not the right shape?

For a handful of values, a dot plot shows every reading. Use a ridgeline to see the shape of a distribution, or a histogram when exact counts per range matter.

Real-world examples

Delivery times

Illustrative delivery times in days for three US cities.

Open in maker with this data

View the spec 
{
  "type": "boxplot",
  "theme": "editorial",
  "title": "How long do orders take to arrive?",
  "source": "Illustrative data · days",
  "data": {
    "labels": [],
    "series": [],
    "groups": [
      {
        "id": "g0",
        "label": "Austin",
        "observations": [
          2,
          2,
          3,
          3,
          3,
          4,
          4,
          4,
          5,
          5,
          6,
          7
        ]
      },
      {
        "id": "g1",
        "label": "Denver",
        "observations": [
          1,
          2,
          3,
          3,
          4,
          4,
          5,
          5,
          6,
          7,
          8,
          9
        ]
      },
      {
        "id": "g2",
        "label": "Miami",
        "observations": [
          3,
          4,
          5,
          5,
          6,
          6,
          6,
          7,
          7,
          8,
          10,
          13
        ]
      }
    ]
  }
}

Salaries by team

Illustrative annual salaries in thousands of US dollars.

Open in maker with this data

View the spec 
{
  "type": "boxplot",
  "theme": "editorial",
  "title": "Where do salaries sit on each team?",
  "source": "Illustrative data · annual salary, USD",
  "data": {
    "labels": [],
    "series": [],
    "groups": [
      {
        "id": "g0",
        "label": "Support",
        "observations": [
          48,
          50,
          52,
          53,
          55,
          56,
          58,
          60,
          61,
          63
        ]
      },
      {
        "id": "g1",
        "label": "Design",
        "observations": [
          62,
          66,
          70,
          72,
          75,
          78,
          80,
          84,
          88,
          95
        ]
      },
      {
        "id": "g2",
        "label": "Engineering",
        "observations": [
          85,
          92,
          98,
          104,
          110,
          115,
          120,
          128,
          135,
          190
        ]
      }
    ]
  },
  "options": {
    "format": "affix:[\"$\",\"k\"]"
  }
}
Open this chart in a maker Box plot maker from scratch

Questions people ask

How are the quartiles calculated?

Standard uses the same method as Excel's QUARTILE.INC. School splits the sorted values into a lower and an upper half, leaving out the median when the count is odd, and takes the median of each half — the method of the TI-84 and most textbooks. The median is the same in both.

What counts as an outlier?

By default, any value more than 1.5 times the box's width below the box or above it. Whiskers reach the lowest and highest values inside that range. Choose Min–max to draw whiskers to the extremes with no outliers.

What happens with missing values?

No data or a blank value is counted as missing, never as zero. The tooltip and the maker's summary say how many values are missing. A group with no values stays visible with a No data label.