How big is The Sun?
The Sun: 1,392,700 km (4,569,225,722 ft). Measured as diameter — mean diameter.
Source: Wikipedia — Sun
Where it sits
Among the 16 planets & moons on this page the Sun ranks 1st from the top by size. Nothing else in its group is bigger here, and the smallest, Ceres at 939 km, is 1,483× smaller.
Stand an adult of 1.7 m beside it and the ratio is 819,235,294×: you would need 819,235,294 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. The Sun is 13,263,810× that, which puts it at 13,263,810 pitch lengths from end to end.
Light covers its diameter in 4.6 seconds. A jet cruising at 900 km/h would need 64.5 days to fly the same distance in a straight line.
Next to its neighbours in size
The nearest thing smaller is Jupiter at 142,984 km (469,107,612 ft), so the Sun is 9.74× as big as it. They sit in the same group.
Against fixed yardsticks
Against three fixed yardsticks — the Sun is 4,220,303× the size of Eiffel Tower (330 m); the Sun is 46,578,595× the size of blue whale (29.9 m); the Sun is 109× the size of Earth (12,742 km).
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 the Sun?
1,392,700 km (4,569,225,722 ft), measured as diameter: mean diameter.
Where does the Sun rank among planets & moons?
Number 1 of 16 on this site, from the Sun at 1,392,700 km down to Ceres at 939 km.
What is the next size down?
Jupiter, at 142,984 km, is 9.74× 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.