I know the maximum transaction size for a BLOCK is 250,000 bytes. My question is a little different.

What is a recommended transaction size for best selection of the transaction by pools? For example say I have 500,000 bytes of transaction to send over the network. How should I chunk those transactions? 50,000 byte transactions? 10,000 byte transactions?

2 Answers 2


It's not about size, it's about fee. If you can have a high enough fee to make a massively sized transaction be incentived to miners, your good. See transaction priority for what I mean.

  • I understand what you are saying about fees... Perhaps I'm over thinking it. My assumption is that large transactions might have a harder time getting included in a block because the block may be filled with a number of smaller transactions. Thus, there should be an equilibrium point where over that point (this is the point I'm trying to ascertain) it becomes harder to include large transaction in a block
    – user789235
    Jan 10, 2014 at 14:24

If you are trying to minimize your expenses from sending transaction, consider this bit from https://en.bitcoin.it/wiki/Transaction_fees


A transaction may be safely sent without fees if these conditions are met:

It is smaller than 1,000 bytes.

All outputs are 0.01 BTC or larger.

Its priority is large enough (see the Technical Info section below)

Otherwise, the reference implementation will round up the transaction size to the next thousand bytes and add a fee of 0.1 mBTC (0.0001 BTC) per thousand bytes[1]. As an example, a fee of 0.1 mBTC (0.0001 BTC) would be added to a 746 byte transaction, and a fee of 0.2 mBTC (0.0002 BTC) would be added to a 1001 byte transaction. Users may increase the default 0.0001 BTC/kB fee setting, but cannot control transaction fees for each transaction.

Bitcoin-Qt does prompt the user to accept the fee before the transaction is sent (they may cancel the transaction if they are not willing to pay the fee).

Note that a typical transaction is 500 bytes, so the typical transaction fee for low-priority transactions is 0.1 mBTC (0.0001 BTC), regardless of the number of bitcoins sent.

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