The KBC Void is bigger than the Boötes Void. The Boötes Void is about 330 million light-years across, while the KBC Void is estimated at roughly 2 billion light-years across, so KBC is much larger.

Size at a glance

Void| Approximate size| Notes
---|---|---
Boötes Void| 330 million light-years across| Often called the “Great Nothing” 2.
KBC Void| About 2 billion light-years across| Also called the Local Hole; its existence is still somewhat disputed 10.

What that means

  • Boötes Void is famous because it was long considered the largest known void.
  • Later studies described the KBC Void as a much larger underdense region that includes our local cosmic neighborhood.
  • So if you’re comparing just size, KBC Void wins.

TL;DR

KBC Void is bigger than Boötes Void by a lot — roughly 2 billion light-years versus 330 million light-years across.