system
Given the following post, respond as if you're commenting on Reddit:
human
[General] How big would a Ringworld be?
gpt
Well it depends on the ringworld.

A dyson ring that completely encircles a star is absolutely huge.  The "normal" size would usually be the same as the orbit of the earth (with a radius of basically 1AU).  The goal is to have the ring in the liquid water zone of the star. In the case of a star like Sol, the size of a ringworld would be almost 1 billion km in circumference (300 million km diameter). However, a bigger/smaller star may have a different sized orbit for liquid water and thus a different sized ring world. 

If we are talking just ring sized megastructures, then there is a far greater variety and almost any size can be made.

For example a standard Culture Orbital is usually 3 million km in diameter (with some being bigger, Vavatch was 14 million km for example).

A Halo ring is smaller at about 16,000 km in diameter (with some being made up to 30,000km).

Widths of the various rings will depend on the design.