Block Size

Overview

Block size affects propagation, storage, and how many transactions can fit in a block. A larger block can include more data, but every validating node must receive and process that data.

Bitcoin distinguishes raw serialized size from block weight. Witness data is discounted in the weight calculation, so the maximum raw size and maximum weight are not identical. Ethereum uses gas limits for execution and separate rules for blob data, so “block size” alone does not describe its full capacity.

When demand exceeds available block space, transactions compete through fees and producer policies. Increasing block size can increase throughput, but it may also raise hardware and bandwidth requirements, potentially reducing the number of independent nodes.

For payments, block-size pressure is visible through higher network fees and longer inclusion times. The effect varies across networks and transaction types.

A larger block can contain more activity, but it also takes longer to transmit and requires more resources to validate and store. If requirements grow too high, fewer participants may be able to run independent nodes, weakening decentralization.

Some protocols separate several capacity dimensions. Bitcoin uses block weight rather than a simple byte limit for consensus accounting, while Ethereum uses execution gas and separate blob capacity. Compression and batching can increase the number of user actions represented without proportionally increasing base-layer size. Performance comparisons should therefore explain which measurement is being used and whether the number reflects a hard limit, a target, or an observed average.

Historical averages can be misleading when a protocol permits temporary bursts or uses a target below the maximum. Capacity analysis should compare both utilization and the rule that limits additional inclusion.