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Encyclopedia How the network works · Entry 80

Bitcoin coin selection: which UTXOs a wallet spends

AI-assisted research · separate automated verificationCorrections

Theme
How the network works
Sources
5 cited records
Reading time
About 3 minutes
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In this article

At a glance

Key facts

Key facts for Bitcoin coin selection: which UTXOs a wallet spends
FactDetailSource
InputsA transaction can spend several outputs received at different times.[2]
CostMore signing data generally changes transaction weight and fee requirements.[4]
ControlThe cited funding RPC can take explicit inputs or select additional ones.[1]
01

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.

02

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.

03

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.

Direct answers

Questions people ask

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.

Inspect the evidence

The answer and key facts have stable claim links. These records retain the scope and qualification when reused.

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: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T18:15:23.891Z.

Link to this claim
Inputs: A transaction can spend several outputs received at different times.

Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T18:15:23.891Z.

Link to this claim
Cost: More signing data generally changes transaction weight and fee requirements.

Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T18:15:23.891Z.

Link to this claim
Control: The cited funding RPC can take explicit inputs or select additional ones.

Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T18:15:23.891Z.

Link to this claim
Revision history
  1. — Initial Bitcoin encyclopedia entry at this permanent URL.
  2. — Added reusable claims, explicit source locators, and matching Markdown and JSON. This publishing change does not itself establish factual verification.

Source register

Sources and references

Retrieval dates and locators are recorded individually.
  1. walletcreatefundedpsbt RPCBitcoin Core

    Input selection, fee units, change output, selected inputs and transaction funding.

    Locator: Arguments and result fields · Version / scope: Bitcoin Core 29.0.0 RPC · Retrieved: 2026-10-02T17:03:40.827ZOpen source
  2. Bitcoin Developer Guide: TransactionsBitcoin developer documentation contributors

    UTXO inputs, transaction outputs, change and the difference paid as a fee.

    Locator: P2PKH Script Validation; Transaction Fees And Change · Retrieved: 2026-10-02T17:03:41.190ZOpen source
  3. Bitcoin Developer Guide: WalletsBitcoin 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: 2026-10-02T17:03:41.163ZOpen source
  4. Segregated Witness consensus layerBitcoin BIPs contributors

    Transaction weight and virtual-size definitions in the SegWit specification.

    Locator: Block size; Transaction size · Version / scope: BIP-141; immutable revision pinned in source URL · Retrieved: 2026-10-02T17:22:20.465ZOpen source
  5. Bitcoin: A Peer-to-Peer Electronic Cash SystemSatoshi Nakamoto

    Most-work chain selection, Merkle inclusion, SPV limits and transaction change.

    Locator: Sections 4–5 and 7–11 · Version / scope: 2008 paper · Retrieved: 2026-10-02T17:03:41.335ZOpen source
How this article was made

Research and drafting use AI assistance. A separate automated review checks claims against primary sources; no external expert or named human review is implied. Publication, substantive editing, source retrieval and verification are recorded separately. This version was independently checked by an automated reviewer on 2 October 2026.

Editorial method and corrections

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/