The satoshi is named after Bitcoin's pseudonymous creator and is defined directly in the protocol: one bitcoin equals 100,000,000 satoshis, making a satoshi worth 0.00000001 BTC. This is the smallest unit the base protocol can represent in a standard on-chain transaction; there is no smaller subdivision at that layer.
This granularity exists because bitcoin's total supply is capped at 21 million, a number chosen for the coin count, not for the total number of spendable units. With 100 million sats per coin, the network can represent roughly 2.1 quadrillion individual satoshis, which keeps the system usable for very small payments even as the price of a whole bitcoin rises.
Because bitcoin's price has risen substantially over its history, many people fall into what is sometimes called "unit bias": feeling that owning "only" 0.001 BTC is somehow less meaningful than owning "1" of some other asset, even when the actual monetary value is identical. Thinking and quoting prices in satoshis is one way people avoid that psychological trap and reason more directly about actual amounts.
Explain more simply
A satoshi, or "sat", is the smallest piece bitcoin can be divided into. There are 100,000,000 satoshis in one bitcoin, the same way there are 100 cents in a euro, except bitcoin has far more decimal places.
You do not need to own a whole bitcoin to use it. Most everyday amounts of bitcoin are actually described in sats, since a whole bitcoin is a fairly large amount of value.
Real-world analogy
Thinking in whole bitcoin when the price is high is like insisting on quoting grocery prices in kilograms of gold, technically correct, but sats are the grams that actually fit everyday transactions.
Key facts
- One bitcoin equals 100,000,000 satoshis.
- A satoshi (0.00000001 BTC) is the smallest unit representable in a standard on-chain transaction.
- The protocol internally counts satoshis as integers to avoid rounding errors.
Common misconception
“You need to buy a whole bitcoin for it to be worth anything.”
Bitcoin is divisible to 100,000,000 units per coin. Owning a fraction of a bitcoin, expressed in satoshis, represents real, proportional monetary value, there is no minimum whole-coin requirement.[1]
Go deeper
Internally, Bitcoin Core and the consensus rules represent amounts as integer counts of satoshis rather than as decimal fractions of a bitcoin, which avoids floating-point rounding errors when validating transactions. The "BTC" figure shown in wallets is a display convenience layered on top of that integer accounting.
Below the satoshi, some protocols and discussions reference even smaller notional units, such as the millisatoshi used internally by the Lightning Network for routing fee calculations, but these do not exist as spendable units on the base Bitcoin blockchain itself.
Quick check
Answer every question correctly (100%) to complete this lesson.
1.How many satoshis make up one bitcoin?
2.What is 'unit bias' in the context of bitcoin?
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Extra exam questions
Every question here counts towards your accuracy, XP and rank. No guessing: every answer is explained.
Quick check
Answer every question correctly (100%) to complete this lesson.
1.What is a satoshi?
2.How many satoshis make up one bitcoin?
3.After whom is the satoshi unit named?
4.Why does bitcoin need a subunit like the satoshi?
5.Is the number of decimal places for bitcoin (eight) a coincidence or a protocol design choice?
6.Can bitcoin transaction amounts be denominated in fractions smaller than a whole bitcoin?
7.Are block subsidy calculations in the Bitcoin protocol done in whole bitcoin or in satoshis?
8.What is often used as a common shorthand nickname for a satoshi?
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Sources
- Bitcoin: A Peer-to-Peer Electronic Cash System (2008), Satoshi Nakamoto
The original nine-page proposal. Describes proof of work, timestamping and the incentive model.
- Bitcoin Core documentation, Bitcoin Core project
Reference implementation documentation, including validation and release notes.