Plot your Transaction in the Mempool

Estimate when your transaction is going to confirm and calculate how much you will spend in Bitcoin transaction fees.

How do I use this?

Alternatively, fill your transaction details below.
inputs  
outputs

sat/vbyte  

Address Format (If you have multiple formats, select the most common input address format.)


Current Mempool
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How bitcoin transactions work? What is the mempool?

When you send a bitcoin transaction, it is broadcasted to all nodes in the bitcoin network. And then it goes to the mempool. The mempool is a collection of unconfirmed transactions waiting to get into the next blocks. A transaction is only confirmed when it is registered in a block.

Why is transaction size important?

A block has a limited block size. Maximum block size is 1 vMB (virtual Megabyte) and it cannot fit all transactions in the mempool at once. To get into a block, you will need to pay a fee per each vbyte of your transaction, also known as fee rate. Fee rate is measured in satoshis per vbyte, or just sat/vbyte.

Miners usually prioritize transactions with a high fee rate to get in the next block. Thus, transactions form a queue in the mempool waiting to get into a block (i.e get a confirmation), such that transactions that pay more per vbyte are confirmed beforehand.

What is this chart and how is the Optimum Fee calculated?

The chart above represents the transactions in the mempool sorted by their fee rate. Transactions paying more fee per vbyte are on the top and will get into the next blocks sooner than transactions on the bottom.

The white lines show the virtual size of the next three blocks. As more transactions are always being broadcasted to the mempool, a feerate inside the next block limit does not guarantee that it will be confirmed soon, but it is a good estimate.

The Optimum Fee is the lowest fee inside the next block, plus 5 sat/vbyte. This code underestimate fees in some situations, so do not use this fee if you need a confirmation in the next block.

How is transaction size calculated?

Every input and output has a size, and that size depends on its respective address format. This tool calculates the size of bitcoin transactions (in vbytes). You just need to enter the number of inputs and outputs, your address format, and choose a fee per byte.

Your transaction size and cost are displayed in BTC and USD value. Compare the value with the size of the next two blocks (marked in the chart) and estimate the transaction fee you want to pay.

How do I pay less in fees?

There are 3 things that control a transaction fee:

You need to make your transaction as small as possible. Reducing the number of inputs and outputs will help. Use segwit, especially Bech32 address formats and choose the fee rate (if you are not in hurry, use a low fee/vbyte).

Further Reading and References:

Weight Units in Bitcoin Wiki.
Segregated Witness (SegWit) in Bitcoin Wiki.

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