# Bitcoin coin selection: which UTXOs a wallet spends Coin selection chooses the UTXOs a Bitcoin wallet will spend to fund a payment and its fee. Different choices can change input count, transaction weight, change outputs and which earlier receipts become linked. The smallest number of inputs is not always the best choice for every wallet objective. Evidence: [walletcreatefundedpsbt RPC](https://bitcoincore.org/en/doc/29.0.0/rpc/wallet/walletcreatefundedpsbt/); [Bitcoin Developer Guide: Transactions](https://developer.bitcoin.org/devguide/transactions.html); [Bitcoin Developer Guide: Wallets](https://developer.bitcoin.org/devguide/wallets.html) Canonical: https://degreesofsatoshi.com/encyclopedia/bitcoin-coin-selection/ Published: 2026-10-02 Substantively modified: 2026-10-02 Independently verified by an automated reviewer: 2026-10-02T18:15:23.891Z Data current through: 2026-10-02 AI-assisted research and drafting with a separate automated source-verification pass; no external expert or named human review is implied. ## Key facts - **Inputs:** A transaction can spend several outputs received at different times. ([Bitcoin Developer Guide: Transactions](https://developer.bitcoin.org/devguide/transactions.html)) - **Cost:** More signing data generally changes transaction weight and fee requirements. ([Segregated Witness consensus layer](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0141.mediawiki)) - **Control:** The cited funding RPC can take explicit inputs or select additional ones. ([walletcreatefundedpsbt RPC](https://bitcoincore.org/en/doc/29.0.0/rpc/wallet/walletcreatefundedpsbt/)) ## The same balance can fund different transactions A wallet holding ten 10,000-satoshi UTXOs has a total of 100,000 satoshis. A second wallet may hold one 100,000-satoshi UTXO. Their displayed balances match, but their options for funding a large payment and the signing data required can differ. Selection must leave enough value for the payment and fee. The fee estimate itself depends on the chosen input types, outputs and expected signed size. Evidence: [Bitcoin Developer Guide: Transactions](https://developer.bitcoin.org/devguide/transactions.html) ## Fees and privacy pull in different directions Combining many receipts can simplify later spending but puts them together in one public transaction. Observers may use that relationship as evidence when clustering activity, although such heuristics are not proof of a person’s identity. Selecting a larger input may create change; an exact-value selection may avoid it. The immediate fee, future cost of spending change and privacy consequences are different considerations. Evidence: [Bitcoin Developer Guide: Wallets](https://developer.bitcoin.org/devguide/wallets.html); [Segregated Witness consensus layer](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0141.mediawiki); [Bitcoin: A Peer-to-Peer Electronic Cash System](https://bitcoin.org/bitcoin.pdf) ## Read the funded result The Bitcoin Core 29.0 funding RPC reports a fee and change position, and accepts options for input selection and fee subtraction. These fields make a useful review checklist even if another wallet exposes them differently. An estimated transaction is not signed authorization. Recheck the final outputs and fee before signing, particularly if a wallet had to add another input. Evidence: [walletcreatefundedpsbt RPC](https://bitcoincore.org/en/doc/29.0.0/rpc/wallet/walletcreatefundedpsbt/) ## Questions ### Does a bigger wallet balance always mean a cheaper payment? No. The relevant input structure and transaction size can differ even when two wallets have the same total balance. Evidence: [Bitcoin Developer Guide: Transactions](https://developer.bitcoin.org/devguide/transactions.html); [Segregated Witness consensus layer](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0141.mediawiki) ## Claims and scope ### bitcoin-coin-selection-quick-answer Coin selection chooses the UTXOs a Bitcoin wallet will spend to fund a payment and its fee. Different choices can change input count, transaction weight, change outputs and which earlier receipts become linked. The smallest number of inputs is not always the best choice for every wallet objective. Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ### bitcoin-coin-selection-fact-inputs Inputs: A transaction can spend several outputs received at different times. Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ### bitcoin-coin-selection-fact-cost Cost: More signing data generally changes transaction weight and fee requirements. Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ### bitcoin-coin-selection-fact-control Control: The cited funding RPC can take explicit inputs or select additional ones. Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ## Sources - [walletcreatefundedpsbt RPC](https://bitcoincore.org/en/doc/29.0.0/rpc/wallet/walletcreatefundedpsbt/) — Bitcoin Core. Input selection, fee units, change output, selected inputs and transaction funding. Locator: Arguments and result fields. Retrieved: 2026-10-02T17:03:40.827Z. - [Bitcoin Developer Guide: Transactions](https://developer.bitcoin.org/devguide/transactions.html) — Bitcoin developer documentation contributors. UTXO inputs, transaction outputs, change and the difference paid as a fee. Locator: P2PKH Script Validation; Transaction Fees And Change. Retrieved: 2026-10-02T17:03:41.190Z. - [Bitcoin Developer Guide: Wallets](https://developer.bitcoin.org/devguide/wallets.html) — Bitcoin developer documentation contributors. Spending keys, address derivation, backups and privacy trade-offs. Locator: Wallet Programs; Public Key Distribution-Only Wallets; Hierarchical Deterministic Key Creation. Retrieved: 2026-10-02T17:03:41.163Z. - [Segregated Witness consensus layer](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0141.mediawiki) — Bitcoin BIPs contributors. Transaction weight and virtual-size definitions in the SegWit specification. Locator: Block size; Transaction size. Retrieved: 2026-10-02T17:22:20.465Z. - [Bitcoin: A Peer-to-Peer Electronic Cash System](https://bitcoin.org/bitcoin.pdf) — Satoshi Nakamoto. Most-work chain selection, Merkle inclusion, SPV limits and transaction change. Locator: Sections 4–5 and 7–11. Retrieved: 2026-10-02T17:03:41.335Z. ## Revision history - 2026-10-02: Initial Bitcoin encyclopedia entry at this permanent URL. - 2026-10-02: Added reusable claims, explicit source locators, and matching Markdown and JSON. This publishing change does not itself establish factual verification. ## Cite this entry Degrees of Satoshi editorial project. “Bitcoin coin selection: which UTXOs a wallet spends.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/bitcoin-coin-selection/