How big is Pluto?
Pluto: 2,377 km (7,797,244 ft). Measured as diameter — mean diameter.
Source: Wikipedia — Pluto
Where it sits
Among the 16 planets & moons on this page Pluto ranks 15th from the top by size. The largest in the group is the Sun at 1,392,700 km, which is 586× the size of Pluto, while the smallest, Ceres, is 939 km.
Stand an adult of 1.7 m beside it and the ratio is 1,398,000×: you would need 1,398,000 people stacked head to foot to match its width — roughly a crowd the size of a small town standing on each other.
In everyday distances
A football pitch is about 105 m long. Pluto is 22,634× that, which puts it at 22,634 pitch lengths from end to end.
Light covers its diameter in 8 milliseconds. A jet cruising at 900 km/h would need 2.6 hours to fly the same distance in a straight line.
Next to its neighbours in size
The nearest thing larger than it in this collection is Europa at 3,122 km (10,241,470 ft), 1.31× the size. Both figures are the same kind of measurement, so the gap is a fair one.
The nearest thing smaller is Ceres at 939 km (3,082,021 ft), so Pluto is 2.53× as big as it. They sit in the same group.
Against fixed yardsticks
Against three fixed yardsticks — Pluto is 7,202× the size of Eiffel Tower (330 m); Pluto is 79,485× the size of blue whale (29.9 m); Earth (12,742 km) is 5.36× the size of Pluto.
How this figure was taken
Worlds are listed by diameter. Gas giants are not round, so equatorial diameter is used for them and mean diameter for the rest. All figures are rounded from published mission data.
How the sizes are taken. Each figure says what it measures — height, length, diameter or elevation — and for which individual or convention. Everything is drawn standing upright on one baseline so a single scale holds, including things that are long rather than tall. Values come from the linked Wikipedia article for each item.
Read the rest — common questions
How big is Pluto?
2,377 km (7,797,244 ft), measured as diameter: mean diameter.
Where does Pluto rank among planets & moons?
Number 15 of 16 on this site, from the Sun at 1,392,700 km down to Ceres at 939 km.
What is the next size up?
Europa, at 3,122 km, is 1.31× the size.
What is the next size down?
Ceres, at 939 km, is 2.53× smaller.
How reliable is the figure?
It is taken from the cited Wikipedia article and states its basis (mean diameter). Values are rounded, and where individuals differ the figure is a representative one, so expect small differences from other sources.