What is a vByte?

A vByte (short for “virtual byte”) is a unit of measurement used to calculate Bitcoin transaction fees after the Segregated Witness (SegWit) upgrade. It’s essentially a simplified way to represent a transaction’s “weight” on the blockchain.

Why do we use vBytes?

• Prior to SegWit, fees were based on a transaction’s raw size in bytes. After SegWit, part of the transaction (the witness data) was discounted, so actual “bytes” alone weren’t an accurate basis for fees.
• To address this, Bitcoin introduced the concept of “weight units” (WU). Every transaction has a total weight, which counts non-witness data more heavily than witness data.
• A vByte is a more user-friendly way to represent a transaction’s weight. Essentially:

  vSize = (3 × non-witness bytes + total bytes) / 4

  This vSize result in vBytes is what most wallets and explorers use when determining the fee in satoshi per vByte (sat/vByte).

Key Takeaway

vBytes simplify fee calculations by assigning a single, “virtual size” to each transaction, regardless of how much of its data is witness vs. non-witness. When you see a fee expressed in sat/vByte, it’s using these vBytes, not literal bytes.