Tools · Privacy-first

Fee & Transaction Size Calculator

Model a Bitcoin transaction before a wallet builds it. Choose the types and counts of inputs and outputs to estimate serialized size, weight, virtual size, and the total fee across three fee-rate scenarios.

The calculator focuses on common single-signature spends and reports an interval where signature length can vary. It does not inspect wallet data, select coins, fetch fee recommendations, or predict confirmation time.

Runs locally

Your transaction plan stays in this browser.

Local input: Input and output counts, fee-rate scenarios, and an optional manually entered BTC price. Network effect: None when calculating. Values are processed in this page, are not sent to BitcoinStats, and are not stored or added to the URL.

Transaction shape + rates Browser calculation Size + fee estimates

After this page has loaded, calculations continue without internet access. Reloading while offline depends on whether your browser retained the page assets in cache.

Transaction model

Build the transaction shape

Input type describes the output being spent. Output type describes each new destination or change output. Amounts, addresses, txids, and keys are not needed.

Presets:

Inputs being spent

Common key-path and single-key spends only.

P2PKHLegacy · ~146–148 base bytes P2SH-P2WPKHNested SegWit · single key P2WPKHNative SegWit v0 · single key P2TR key pathTaproot · no annex

New outputs

Include the recipient and any change output.

P2PKH34 bytes each P2SH32 bytes each P2WPKH31 bytes each P2WSH43 bytes each P2TR43 bytes each OP_RETURNUnspendable data output Payload bytes per OP_RETURN0–1,000,000 bytes · serialization model

Fee-rate scenarios

Enter your own rates. These labels do not imply a confirmation target.

Scenario Asat/vB Scenario Bsat/vB Scenario Csat/vB

Optional fiat display

Manual BTC price only; no market API is contacted.

Price per BTC Currency

Default model: one native SegWit input, one payment output, and one change output.

Estimated virtual size—

Fee comparison

Same transaction, three fee rates

Fees are calculated as ceil(vsize × fee rate). A wallet may build a different transaction, add or remove change, select another input type, or use a different signature size. Fee rate alone never guarantees when a transaction will confirm.

Serialization breakdown

Where the bytes and weight come from

Component	Count	Base bytes	Witness bytes	Weight

Purpose and limits

Use the estimate as a planning range

Compare transaction shapes

See how adding inputs, change, or batched outputs changes weight and total fees before exposing any wallet details.

Signature-aware intervals

ECDSA spends assume common 70–72-byte signatures including the sighash byte. Taproot key-path spends cover 64–65-byte signatures. Rare shorter DER signatures can make an actual transaction smaller.

Serialization is not relay

OP_RETURN payloads up to 1,000,000 bytes can be modeled. The result flags major Core policy and consensus boundaries, but peer and miner policy still determines propagation and inclusion.

Weight and witness serialization follow BIP141. The Taproot key-path signature range follows BIP341. OP_RETURN payloads are modeled as one minimally encoded data push, including PUSHDATA and CompactSize boundaries. The historic 80-byte payload ceiling was relay policy, not a consensus limit. P2WSH and P2TR script-path outputs can be counted because their output sizes are fixed, but spending them later requires a script-specific estimate that is intentionally outside this calculator.