# Child pays for parent (CPFP)

CPFP speeds up a stuck Bitcoin transaction by spending its output in a new high-fee child. Miners take both together. Learn when and how to use it.

Canonical page: https://mybitcoinexplorer.com/learn/child-pays-for-parent-cpfp
Topic: Transactions
Published: 2026-10-29
Updated: 2026-10-30


## The trick
A child transaction can only confirm if its parent confirms first, in the same block or earlier. So if you spend an output of a stuck transaction with a **high fee**, a miner who wants that fee must include the parent too.

> Diagram: The child's high fee lifts the parent: miners evaluate them as a package — 

### Worked example: Working out the package rate
Parent: 200 vB paying 400 sats (2 sat/vB). Child: 150 vB paying 6,000 sats (40 sat/vB). Together: 6,400 sats ÷ 350 vB ≈ **18.3 sat/vB**. If that beats the current next-block rate, a miner is likely to take both.


## Who can use it?
Anyone who controls an output of the stuck transaction:
- the **receiver**, spending the payment they got,
- the **sender**, spending their [change](https://mybitcoinexplorer.com/learn/change-outputs).

That's the advantage over [RBF](https://mybitcoinexplorer.com/learn/replace-by-fee-rbf), which only the sender can use.

> CPFP uses more block space than RBF because it adds a whole new transaction.


## Working out the child's fee
To lift a stuck parent to a target package rate:

~~~
child fee = target rate × (parent vsize + child vsize) − parent fee
~~~

With a 200 vB parent paying 400 sats, a 150 vB child and a 15 sat/vB target: 15 × 350 − 400 = **4,850 sats** for the child.

## When to choose CPFP over RBF
- You're the **receiver** and can't replace the sender's transaction.
- The sender didn't allow replacement and your wallet won't override it.
- You want to keep the original transaction exactly as it is.


## Key takeaways

- A high-fee child transaction pulls its low-fee parent into a block.
- Miners look at the combined package fee rate.
- Receivers can use CPFP; only senders can use RBF.

## Common questions

### Does CPFP always work?

Usually, but very large unconfirmed chains or a parent far below the minimum relay fee can cause problems.

### Is CPFP more expensive than RBF?

It usually costs a bit more because the child transaction takes extra space.

### Can anyone do CPFP on my transaction?

Only someone who controls one of its outputs: usually the receiver or the sender via their change.

### Is CPFP supported by wallets?

Several desktop wallets offer it, often labelled 'accelerate' or 'CPFP' on unconfirmed incoming payments.

## Related lessons

- [Replace-by-fee (RBF)](https://mybitcoinexplorer.com/learn/replace-by-fee-rbf)
- [Fee rate: sats per vbyte](https://mybitcoinexplorer.com/learn/fee-rate-sat-per-vbyte)
- [What is the Bitcoin mempool?](https://mybitcoinexplorer.com/learn/what-is-the-mempool)
- [How Bitcoin transaction fees work](https://mybitcoinexplorer.com/learn/bitcoin-transaction-fees)