# How long is a Bitcoin?

I searched already but I couldn't find anything about the structure of a bitcoin.

My understanding is that a bitcoin, which is different AFAIK from a bitcoin address, can be interpreted as a string of numbers and characters (alphanumeric). How long is a bitcoin string (min/max)?

I found here (https://blockexplorer.com/block/000000000000000002109f32aeac7a036232b0116f939326651e739a28e6d6b6) now a size of: 934325 bytes for a particular bitcoin. Could this be the length of the particular bitcoin?

PS: I searched always for length and not for size...

• the size you have there is the size of the block and all of the transactions included in it – Mark S. May 24 '16 at 16:04

A bitcoin is not a piece of data, and therefore does not have a length. A bitcoin, the unit of currency, is just like any other unit of measurement. It wouldn't make sense to ask "how much data is a meter?", and likewise it doesn't make sense to ask how long a bitcoin is.

That said, the amount of bitcoin that is stored by an individual is the sum of all the bitcoin denoted in the unspent transaction outputs (UTXOs) that are controlled by the individual. These are pieces of data and do have a size...albeit a variable one. These outputs do not need to be stored by the owner, as they are stored on the blockchain. All the owner needs to store is private keys that allow them to spend the UTXOs, which is what a wallet manages for you.

I hope that helps.

• +1 I started writing an answer, but found that I was essentially reiterating what you wrote. – Murch Jun 1 '16 at 5:40

There is no length or size of a bitcoin, conceptually you just have a value stored in a database (the blockchain) and the encryption keys to validate that you have control over the associated amount of bitcoin. Bitcoins are public and private key pairs. The private key contains 256-bits. This is used to derive a public key (that bitcoin users do not see, but they are published once bitcoins are being spent) and a bitcoin address which users do see and interact with. Bitcoin addresses are base-58 encoded so that there is no confusion between certain characters such as 0 vs O.

• I find the sentence "Bitcoins are public and private key pairs." a bit misleading, perhaps that should be phrased differently. – Murch Jun 1 '16 at 5:42

A Bitcoin address, is an identifier of 26-35 alphanumeric characters, beginning with the number 1 or 3.

Most addresses are 33 or 34 characters long.