Bitcoin Fees Today: Current sat/vB Rates and Mempool Status

How Bitcoin transaction fees work

Every Bitcoin transaction competes for space in the next block. Blocks arrive roughly every ten minutes and hold a limited amount of data, so miners prioritise the transactions offering the most value per byte of space they consume. That price is expressed in satoshis per virtual byte, written sat/vB.

Fee and fee rate are two different numbers

The fee is the total number of satoshis your transaction pays. The fee rate is that total divided by the transaction's size in virtual bytes. Miners rank candidates by fee rate, because block space is what is scarce — so the fee rate decides your position in the queue and the total fee decides what it costs you. Two transactions can pay the same total fee and have completely different prospects.

Nothing in this arithmetic involves the amount of bitcoin being sent. Sending 10 BTC costs no more than sending 0.001 BTC if both transactions are the same size. This is the single most useful thing to know about Bitcoin fees.

Why size varies so much

A transaction's size in virtual bytes depends on how many previous outputs it spends, how many outputs it creates, and which address type those inputs use. Each additional input adds a signature and therefore real bytes; this is why a wallet holding many small amounts pays far more to send the same value than a wallet holding one large amount.

Address type matters too, and it is not a simple legacy-versus-SegWit split. Witness data is discounted when virtual size is calculated, so a legacy (P2PKH) spend is the most expensive per input, nested SegWit (P2SH-P2WPKH) is cheaper, native SegWit (P2WPKH, addresses beginning bc1q) is cheaper again, and single-signature Taproot (P2TR, addresses beginning bc1p) is typically the smallest of the four. Multi-signature and script spends can be considerably larger than any of them. The table above is indicative only — your wallet shows the real size for the transaction it has built.

Why two transactions sending the same amount can pay different fees

• One spends a single large input; the other spends eight small ones and is several times larger in virtual bytes.
• One uses Taproot or native SegWit inputs; the other uses legacy inputs that receive no witness discount.
• One was built during a quiet period and the other while the backlog was deep, so the wallet chose very different fee rates for the same target.
• One creates a change output and the other does not, which changes the size slightly and the wallet's coin-selection choices considerably.

How confirmation priority is decided

Wallets estimate what rate is currently needed to be included within a target number of blocks. High priority aims for the next block, medium for around thirty minutes, low for about an hour, and economy accepts an open-ended wait until the backlog clears. When the mempool is nearly empty these four numbers converge; when it is congested they can differ by an order of magnitude.

Estimates are probabilistic, and they describe conditions at the moment you read them. A rate that was competitive when you broadcast can be overtaken minutes later by transactions that did not exist yet. Choosing a fee is therefore a judgement about urgency: pay the high-priority rate when a delay would actually cost you something, and the economy rate when it would not.

Why low-fee transactions can wait

An underpriced transaction is not broken and not lost. It sits in node mempools while higher-paying transactions are mined ahead of it, and it becomes competitive again whenever demand falls. Nodes may eventually evict or expire it, at which point the coins are simply still yours and unspent — you never paid a fee, because fees are only paid on inclusion in a block. How the mempool queue works.

If your transaction is stuck

Two mechanisms can help, and which applies depends on what you control. Replace-by-fee lets the sender broadcast a higher-paying version of the same transaction, if their wallet supports it. Child pays for parent works by spending one of the stuck transaction's unconfirmed outputs with a high fee, which a recipient can sometimes do. Neither guarantees confirmation, and no third-party "accelerator" service is legitimate.

This page is educational. It is not financial advice, and fee estimates are probabilistic — always confirm the rate in your own wallet before broadcasting.