Block Weight

Block weight is a protocol-specific metric used to determine how much data a block represents under the rules of the blockchain. The concept is particularly associated with Bitcoin following the introduction of SegWit.

Different parts of a transaction can receive different weighting under the protocol rules. This allows witness data and other transaction components to contribute differently to the block-capacity limit.

Weight versus size

Block weight and physical block size in bytes are not interchangeable measurements. A block can have a particular byte size while its protocol-defined weight is calculated using separate rules.

For networks that use block weight, capacity analysis should therefore consider the protocol weight limit rather than relying only on the number of megabytes stored in a block.