Two spreads live in a box plot: the range across the whole diagram and the interquartile range across the box. These free printable worksheets read the marks and subtract for each, with an answer key.
If they get stuck
The answer key prints on a separate page.
The range is the distance from the left whisker end to the right — the largest value minus the smallest — and it uses only the two extremes. The interquartile range is the width of the box, Q3 minus Q1, and it describes the middle half where most of the data actually sits. Reading both off the same picture is what makes the difference between them concrete.
This is the box-plot twin of the interquartile-range sheet, and the difference is where the numbers come from. There, a child orders a list to find the quartiles; here the quartiles are already drawn and the work is reading them off and subtracting. The box being the middle half is the idea worth holding: a wide box means the central values are spread, a narrow one means they are packed together, whatever the whiskers do.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Box plot range and IQR, step by step