# block weight

URL: https://blockspace.wiki/glossary/block-weight/

A block's size as consensus counts it, in [weight units](https://blockspace.wiki/glossary/weight-unit/): every non-witness byte weighs 4 WU and every witness byte 1 WU, and a block may weigh at most 4,000,000 WU.

Because a non-witness byte weighs 4 WU, a block of non-witness bytes alone reaches the limit at 1,000,000 bytes: the "1 MB block" of before SegWit. Witness bytes weigh a quarter as much, so a block carrying mostly witness data, like an inscription, can hold nearly 4 MB. Space Blocks' image of 1,047,584 bytes, more than a pre-SegWit block could hold, sits in one transaction of 1,054,167 WU, 26.4 % of the limit; the largest inscriptions, close to 4 MB, fill nearly a whole block.

Sources:

- block.space docs: data types · https://block.space/docs/datatypes
- The spaceblocks.art site: README, index.html, whole-blocks/ and tools/build.py · https://spaceblocks.art

Updated: 2026-10-20