A Bitcoin fee quote of 5 sat/vB does not mean the payment costs five satoshis. It is a rate for each virtual byte of transaction size. To work out the total network fee, multiply that rate by the transaction’s virtual size; the amount of bitcoin being sent is not the multiplier.
| What you need to know |
|---|
| A fee rate in sat/vB needs a transaction size to produce a total fee. |
| At 5 sat/vB, a hypothetical 200-vB transaction pays 1,000 satoshis. |
| Bitcoin Core's estimatesmartfee reports its rate in BTC/kvB. |
| A confirmation target is an estimate, not a promised arrival time. |
Blockstream’s fee explanation describes fees as the price of transaction space. The total follows from multiplying the rate in satoshis per virtual byte by the size in virtual bytes. A satoshi is one hundred-millionth of a bitcoin. Virtual size is a measure of transaction weight, rather than the value of the payment.
Take a hypothetical transaction of 200 virtual bytes, quoted at 5 sat/vB. Multiplication gives 1,000 satoshis, or 0.00001000 BTC. A second transaction of 400 virtual bytes at that same rate would cost 2,000 satoshis. These are illustrative sizes and rates, not a reading of current network conditions. Doubling the space used doubles the fee while the rate stays unchanged.
Conversely, a total fee of 1,000 satoshis does not identify the rate on its own. Dividing it by 200 vB gives 5 sat/vB; dividing the same total by 400 vB gives 2.5 sat/vB. This is why two total-fee figures cannot establish which payment offered more for each unit of block space. Keep the size alongside the total when comparing them.
Converting the rate before comparing it
Bitcoin Core 30.0’s estimatesmartfee documentation uses BTC/kvB for the returned rate. A kilovirtual byte contains 1,000 virtual bytes, while one BTC contains 100 million satoshis. Converting BTC/kvB to sat/vB therefore means multiplying the displayed number by 100,000: first convert bitcoin to satoshis, then divide by 1,000.
For example, an illustrative response of 0.00005000 BTC/kvB converts to 5 sat/vB. Applied to the same 200-vB example, it gives the same 1,000-satoshi total. Treating 0.00005000 as a total payment fee would instead mean 5,000 satoshis. The unit label decides which operation is valid; the decimal alone is insufficient.
A successful conversion presupposes that a rate was returned. Bitcoin Core describes an approximate fee for a confirmation target in blocks and can return an error if it lacks sufficient transaction and block observations. Its feerate field is present only when no errors were encountered. A response without that field supplies no number to convert; it does not mean a zero-fee payment. When a rate is returned, converting its unit still cannot guarantee when a particular transaction will confirm.
