Dust Limit

The dust limit is a Bitcoin Core relay-policy threshold that rejects transaction outputs whose value is too low to be worth spending. An output is considered "dust" when the fee required to later spend it would exceed roughly a third of the output's own value, calculated at the node's dustRelayFee (default 3,000 sat/kvB). Such outputs are deemed economically meaningless and refused at the mempool relay layer.

Default Thresholds

For a legacy P2PKH output the threshold works out to 546 satoshis; for a SegWit P2WPKH output, whose spending input is cheaper in weight, it is 294 satoshis. The exact figure scales with the input's projected spending cost, so larger or more complex output types carry higher dust thresholds. These are policy values, not consensus rules — a miner could in principle mine a sub-dust output, but standard nodes will not relay or accept the transaction into their mempool.

Why It Exists

The dust limit protects the UTXO set from bloat. Every unspent output consumes memory on every full node indefinitely, so creating outputs that will never economically be spent imposes a permanent cost on the network for no benefit. The rule discourages this externality. Note it is a per-output check applied during standardness validation, distinct from minimum-fee rules.

For sovereign Bitcoiners running nodes, understanding dust matters for UTXO management and avoiding unspendable change. See our entries on Standardness and Mempool Policy for how this threshold fits into Bitcoin Core's broader relay rules.