> ## Documentation Index
> Fetch the complete documentation index at: https://rexrex.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Estimate Replacement Thresholds

> Inspect the local fee bump needed to replace a transaction already in the pool.

Use `txpool replacement` to inspect the fee bump needed to replace a transaction already present in the pool.

The command does not submit a replacement transaction. It reads the target transaction from `txpool_content`, applies a local price-bump percentage, and optionally checks candidate fee flags.

Use [Inspect](/docs/txpool/inspect), [Sender](/docs/txpool/sender), or [Duplicates](/docs/txpool/duplicates) to find the target transaction hash first.

## Show Required Fees

```sh theme={null}
rex txpool replacement \
  --tx 0x9f7e39db6d3da9d80b8578c6e142de4da7886f191e7d326d4e95b67e03ed2305
```

## Example Output

```text theme={null}
TXPOOL REPLACEMENT

Target:     0x9f7e39db6d3da9d80b8578c6e142de4da7886f191e7d326d4e95b67e03ed2305
Sender:     0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
Nonce:      2
Status:     queued
Type:       eip-1559
Price bump: 10%

Current fees:
  gas price                  -
  max fee per gas            1.000 gwei
  max priority fee per gas   1.000 gwei

Minimum replacement fees:
  gas price                  -
  max fee per gas            1.100 gwei
  max priority fee per gas   1.100 gwei
```

## Test Candidate Fees

For an EIP-1559 transaction, provide both `--max-fee-per-gas` and `--max-priority-fee-per-gas`:

```sh theme={null}
rex txpool replacement \
  --tx 0x9f7e39db6d3da9d80b8578c6e142de4da7886f191e7d326d4e95b67e03ed2305 \
  --max-fee-per-gas 1100000000 \
  --max-priority-fee-per-gas 1100000000
```

For a legacy transaction, provide `--gas-price`:

```sh theme={null}
rex txpool replacement \
  --tx 0x... \
  --gas-price 1100000000
```

The default bump is `10%`. Override it when testing a different node policy:

```sh theme={null}
rex txpool replacement \
  --tx 0x... \
  --price-bump-percent 12 \
  --gas-price 1120000000
```

## Limitation

This command is a fee-bump estimate. A node can still reject a replacement for other txpool-policy reasons, and Reth's configured txpool price bump is the final source of truth.


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