Dust Limit

The dust limit is Bitcoin Core's policy threshold below which an output is considered "dust" and the transaction is treated as non-standard, meaning the node won't relay or include it in its mempool.

The exact threshold depends on the output script type, because the calculation accounts for the cost of spending that output later: an output is dust if spending it would cost more in fees than the value being moved. As of 2026:

• P2PKH (legacy): ~546 sats.
• P2SH: ~540 sats.
• P2WPKH (native SegWit): ~294 sats (smaller because SegWit input is smaller).
• P2TR (Taproot): ~330 sats.
• OP_RETURN outputs are exempt because they're provably unspendable (no future spending cost to amortize).

The formula in Bitcoin Core: dust_threshold = (output_size + input_size) * dustRelayFee / 1000, where dustRelayFee defaults to 3,000 sats/kvB. Operators can adjust the fee rate, which changes the threshold proportionally.

What "non-standard" means in practice:

• Default Bitcoin Core nodes won't relay transactions with dust outputs. The transaction is effectively invisible to most of the network.
• Default Bitcoin Core mining policy won't include them in candidate blocks.
• Consensus rules don't reject them. A dust-containing transaction can technically be in a block; the policy is a relay/standardness filter, not a hard rule. Some miners and pools accept dust-containing transactions through out-of-band submission for a fee.

Why the limit exists:

• UTXO set growth. Every output a node stores costs memory. Dust outputs that nobody will ever spend bloat the UTXO set forever.
• Economically rational. If spending an output costs more than the output is worth, no one will ever spend it - it's permanently stuck. Better to never create it in the first place.
• Spam resistance. Tiny outputs are a cheap way to abuse the network. The dust limit raises the cost.

Users typically encounter the dust limit only at the edges - building a transaction with very small change output, or trying to send a tiny amount. The wallet either consolidates the dust into the fee or refuses to build the transaction, depending on the wallet's UX.