Awarded once after a correct answer.
Calculate a fee rate rather than a transfer percentage
Useful first : Bitcoin UTXOs explained · Bitcoin mining and difficulty
Reading path · 7 / 41 · Intermediate
Fees are commonly quoted in satoshis per virtual byte.
The essentials
Fees are commonly quoted in satoshis per virtual byte. A satoshi is one hundred-millionth of a bitcoin; virtual size reflects transaction weight. Cost depends more on transaction structure and competing demand than on the amount transferred. A large-value payment can be cheaper than consolidating many small outputs.
How it works
Nodes maintain their own pools of pending transactions; there is no single authoritative global mempool. A transaction included in the current tip has one confirmation. Each additional block increases the count, but the appropriate acceptance threshold depends on the payment and network conditions.
What to watch
Replace-by-fee and child-pays-for-parent can improve the fee incentive for pending transactions, subject to relevant policies and available outputs. They do not reverse a confirmed payment. Distinguish throughput, time to inclusion and settlement confidence: faster inclusion does not by itself eliminate the possibility of a reorganisation.
Understand the details
Bitcoin fees depend largely on transaction weight and competition for block space. Wallets commonly quote satoshis per virtual byte. A payment of a large amount can be smaller in data size than a small payment consuming many inputs. Fee estimates are forecasts of demand, not reservations guaranteeing a block.
Boundaries and common mistakes
Replacement policies and child-pays-for-parent can help some pending transactions, but support and eligibility vary. A replacement changes the transaction identifier and requires careful recipient tracking. A confirmation policy should also account for value and reorganization risk; paying more affects inclusion incentives rather than making invalid transactions acceptable.
The mechanism at a glance
- 01Transaction size
- 02Multiply by sat/vB
- 03Total offered fee
- 04Inclusion remains uncertain
Read these as connected concepts, not necessarily consecutive steps.
Read the explanation
Bitcoin fees depend largely on transaction weight and competition for block space. Wallets commonly quote satoshis per virtual byte. A payment of a large amount can be smaller in data size than a small payment consuming many inputs. Fee estimates are forecasts of demand, not reservations guaranteeing a block.
Put the mechanism into context
A fictional transaction is 180 virtual bytes. Compare rates of 5 and 20 sat/vB. Calculate each total fee, then explain why neither calculation tells you an exact confirmation time. Do not confuse virtual bytes with the transferred bitcoin amount.
Apply it in the workshop →What this mechanism does not guarantee
Replacement policies and child-pays-for-parent can help some pending transactions, but support and eligibility vary. A replacement changes the transaction identifier and requires careful recipient tracking. A confirmation policy should also account for value and reorganization risk; paying more affects inclusion incentives rather than making invalid transactions acceptable.
The distinction that changes the analysis
A fictional 140-vbyte transaction at 8 sat/vB costs 1,120 satoshis. Doubling its payment amount does not automatically double its virtual size. Compare transaction structure and fee rate rather than applying a percentage to the transferred amount.
Explain it yourself
Revisit the case above. Name what is established, what remains to be checked and the evidence needed to conclude. A strong answer addresses both sides of the diagram.
Apply the lesson to a case
A fictional transaction is 180 virtual bytes. Compare rates of 5 and 20 sat/vB. Calculate each total fee, then explain why neither calculation tells you an exact confirmation time. Do not confuse virtual bytes with the transferred bitcoin amount.
The fees are 900 and 3,600 satoshis. A useful status distinguishes pending, replaced, included and confirmed, links the correct transaction and avoids promising an exact deadline. If the transaction grows by adding inputs, recalculate its size rather than applying the old estimate blindly.
Follow a Bitcoin transaction
Wallet
Select available UTXOs, recipient, change and a fee. This simulation never connects to a wallet.
Terms in this lesson
- Mempool
- A node’s local collection of pending transactions; different nodes can hold different sets.
Prepare a correction note
Describe the passage and the proposed correction. This creates a local note for you to share; it sends nothing. Do not include personal or confidential information.