What is a satoshi, and why is Bitcoin divisible?

For information only. Not investment advice. This guide explains a unit of measurement and makes no prediction about price. Don't invest unless you're prepared to lose all the money you invest.

The short answer

A satoshi is the smallest amount of bitcoin that exists. Bitcoin's software records every balance as a whole number of satoshis, and one bitcoin is simply 100,000,000 of them. The word “bitcoin” is the larger unit people use in conversation, in the same way that pounds are the larger unit and pence the smaller one. The difference is that Bitcoin's smaller unit is a hundred million times smaller than its larger one.

This guide sits in the CoinCorner learn hub. If you are new to the wider picture, start with What is Bitcoin and how does it work?

What a satoshi is

The satoshi, shortened to “sat”, is the base unit of the Bitcoin system. A sat is written as 0.00000001 BTC, which is eight decimal places. The Bitcoin developer documentation describes amounts in terms of satoshis, and the software handles them as whole numbers rather than decimals, which avoids rounding errors in the ledger.

The name honours Satoshi Nakamoto, the pseudonym used for the white paper that described Bitcoin in October 2008. The unit is an informal tribute that the community adopted. It is not a separate asset and it has no link to the wallet of whoever used that name. Whether the unit is called a sat, a satoshi or 0.00000001 BTC, it is the same amount.

Bitcoin and satoshis side by side

Because the relationship is fixed, the conversion is only a matter of moving the decimal point eight places. The table below shows common amounts. It uses no prices because the pound value of any amount changes constantly.

The conversion is arithmetic and nothing more. You can check any row by multiplying the BTC figure by 100,000,000.

Why Bitcoin is divisible

Bitcoin's total supply is capped at 21 million coins. A fixed cap raises an obvious problem: if each coin were indivisible, the system would have only 21 million units to share between everyone who might use it, and the units could become too valuable to be practical for small payments. Dividing each coin into 100,000,000 parts solves this. Multiplying out gives 2,100,000,000,000,000 satoshis, or 2.1 quadrillion, as the maximum number of units in existence.

Divisibility is therefore built into the design from the start, and the same property applies to money in general. A pound is divisible into pence for the same reason: not every purchase costs a round sum. The practical result for a buyer is that the price of a whole bitcoin does not limit how much you can buy. CoinCorner's smallest purchase is £1, which buys a fraction of a coin at the price at that moment. Fees and limits are listed on the fees page.

If more precision were ever wanted, the protocol could in principle be changed to allow smaller units, but that would need broad agreement across the network, as with any change to the rules. Nothing in this guide depends on such a change.

How people use sats in practice

Many wallets and apps let you choose between showing a balance in BTC, in sats or in pounds. Each is a view of the same holding. The choice is mostly about readability: 250,000 sats is easier to read than 0.0025 BTC for some people, and the reverse is true for others.

• Small purchases. The phrase “stacking sats” describes building up a holding in small, regular amounts. The glossary entry gives the short definition. It is a way of describing a habit, not a strategy that reduces risk.
• Fees. Bitcoin network fees are tied to the size of a transaction in data, not to the amount sent, and they are paid in satoshis. How fees and confirmations work is covered in How Bitcoin transactions are confirmed.
• Lightning payments. Small payments over Lightning are commonly priced in sats. The Lightning specifications also use the millisatoshi, one-thousandth of a satoshi, for accounting inside a payment, while on-chain settlement is in whole satoshis. See What is the Lightning Network?

Common misunderstandings

“Sats are a different, cheaper coin”

They are not. A sat is a slice of a bitcoin. Owning 100 million sats is owning one bitcoin, and a number that looks large does not mean a large sum of money.

“Bitcoin is too expensive for me”

The price of a whole coin is not a barrier to buying, because you can buy a fraction. Whether it is suitable for you is a separate question that depends on your circumstances and your appetite for risk.

“Counting in sats makes it safer”

It changes nothing about risk. The price can fall as well as rise, and the FCA warns consumers to be prepared to lose all the money they invest in crypto. Crypto holdings in the UK are generally not covered by the Financial Services Compensation Scheme or the Financial Ombudsman Service.

Holding small amounts safely

Small balances are controlled by the same keys as large ones, so the custody questions are the same: who holds the keys, and what happens if they are lost or compromised. A multi-signature Vault requires more than one key to approve a spend; how the Vault protects your keys explains what that does and does not protect against, and the security page covers how CoinCorner holds customer Bitcoin. CoinCorner Ltd is registered with the Isle of Man Financial Services Authority as a designated business for anti-money-laundering oversight only. That is not a licence, and CoinCorner is not regulated by the FCA. For buying steps, see how to buy Bitcoin in the UK, and for account questions see the FAQ.

Frequently asked questions

Sources

The statements about the unit and the supply cap come from the documents below. This guide was written on 20 October 2026. The links were not re-opened on the day of writing, so please check each point against the original; the 100,000,000-satoshi relationship is a fixed property of the protocol and has not changed since launch.

1. Satoshi Nakamoto, Bitcoin: A Peer-to-Peer Electronic Cash System (2008): https://bitcoin.org/bitcoin.pdf
2. Bitcoin Project, Developer Guides: https://developer.bitcoin.org/devguide/
3. Bitcoin Project, Developer Reference: https://developer.bitcoin.org/reference/
4. Lightning Network specifications (BOLTs): https://github.com/lightning/bolts
5. Financial Conduct Authority, Crypto: The basics: https://www.fca.org.uk/investsmart/crypto-basics