Sats, BTC & units

One bitcoin currently costs $85,533. Does that put you off? You’re not alone. But you don’t have to buy a whole bitcoin – just as you don’t need a kilo bar to own gold.

1 BTC = 100,000,000 sats

One bitcoin can be divided into 100 million equal parts; the number is set as a constant in the program code.^[1] The smallest unit is called a satoshiGlossarySatoshi (sats)The smallest unit of Bitcoin: 1 satoshi (‘sat’ for short) equals 0.00000001 BTC, so one bitcoin consists of 100 million sats. The unit is named after Bitcoin’s creator, Satoshi Nakamoto.On the learning path: Stage 4 · Step 4 – Setting up a savings plan →In the glossary →×, ‘sat’ for short, ‘sats’ in the plural – named after Bitcoin’s inventor, Satoshi Nakamoto.^[2]

The blockchain stores all amounts in sats. ‘BTC’ is just a conversion for display.^[2]

The improvement proposal BIPGlossaryBIP (Bitcoin Improvement Proposal)A publicly documented proposal for Bitcoin – for example for new rules, standards or processes. A BIP is not a decision: whether it gets used is up to users, wallets and node operators themselves.In the glossary →× 176 describes ‘bit’ as a standard term for 100 sats, so that small amounts need fewer decimal places.^[4] In everyday use, however, the sat has caught on. The Lightning NetworkGlossaryLightning NetworkA second layer on top of Bitcoin for fast, low-cost payments. Amounts move off the blockchain via payment channels; only opening and closing a channel ends up in a block as a normal transaction.On the learning path: Stage 1 · Step 3 – How does Bitcoin work? →In the glossary →× uses millisatoshis for very fine-grained payments; they don’t exist on the blockchain.^[2]

The myth that ‘one bitcoin is too expensive’

We tend to see things with a high unit price as expensive and things with a low one as cheap. This fallacy is called ‘unit bias’; BIP 176 lists reducing it, for people who want a ‘whole’ bitcoin, as a possible benefit of the ‘bit’ unit.^[4]

The unit price depends mainly on how many units a system is divided into. Bitcoin is capped at just under 21 million units^[3] – around 2.1 quadrillion sats. If Bitcoin had a thousand times as many units, each would be a thousand times cheaper, but the total value (market capitalisationGlossaryMarket capitalisation (market cap)Circulating supply multiplied by the current price. The figure shows the order of magnitude – not how much money has actually been invested or would come out if everything were sold.On the learning path: Stage 2 · Step 2 – Halving & 21 million →In the glossary →×) would be the same. A token with a unit price of a few cents is therefore not ‘cheaper’ than Bitcoin. How the cap comes about is explained in The halving & the 21 million.

Converting: dollars, BTC and sats

The formula is always the same:

sats = amount in dollars ÷ price × 100,000,000

dollars = sats × price ÷ 100,000,000

For the examples we use an example price of $80,000 per BTC (currently: $85,533). We calculate in US dollars, the usual currency for the Bitcoin price; the formula works the same with euros, pounds or any other currency, as long as the amount and the price are in the same currency (in euros, one bitcoin currently costs €76,470).

At $80,000 you get exactly 1,250 sats for $1; one sat is worth 0.08 cents. At the current price it’s around 1,169 sats per dollar.

Example price $80,000 per BTC, excluding fees.

Conversely, at this price 100,000 sats (0.001 BTC) are worth $80 and one million sats (0.01 BTC) $800. The sats converter works out your own amounts at the current price.

The number stays, the value fluctuates

If you own 100,000 sats, that number stays the same as long as you don’t buy, sell or send any. Their dollar value changes with the price:

• at $80,000 per BTC: $80
• 20% lower, at $64,000: $64
• 20% higher, at $96,000: $96

This volatilityGlossaryVolatilityA measure of how strongly a price fluctuates, usually given as annualised standard deviation in per cent. Bitcoin fluctuates much more than a broad stock index or gold – up and down.On the learning path: Stage 3 · Step 3 – Returns & risk →In the glossary →× is high for Bitcoin. How much the price has fluctuated so far is shown in Bitcoin returns & risk: an honest look.

Small amounts: fees and dust

Fixed fees weigh heavily on small purchases. A made-up example with a flat fee of $0.99 per purchase:

• On $10, that is 9.9% of the amount.
• On $100, it is 0.99%.

Depending on the provider, percentage fees and a mark-up in the price (spreadGlossarySpread (bid-ask spread)The difference between the buy and sell price. With many apps, the spread is the real fee – it just doesn’t appear as a separate item on your statement.On the learning path: Stage 4 · Step 2 – Choosing a provider →In the glossary →×) come on top. The types of cost are explained in Understanding the fees; you can compare models in the fee calculator.

Sending is different: the network fee doesn’t depend on the amount, but on the transaction’s data size and the demand for space in the block.^[5] For a small amount it can therefore be disproportionately high. More on this in Transactions & fees.

Very small amounts can hardly be sent on the blockchain at all. Nodes with default settings don’t relay transactions that send an amount below the dust limit; depending on the address type, it lies between 294 and 546 sats.^[6] The Lightning Network is designed for amounts like these.

What this looks like in an app

Many apps and wallets can show amounts in BTC or in sats. The screens show a generic example app, not a real provider.

Notation and pitfalls

• Comma or point: English-language apps write 0.00062 BTC and 62,000 sats; German-language apps write 0,00062 BTC and 62.000 sats, and many other European languages also use a decimal comma. Keep this in mind when you transfer amounts between apps.
• At most eight decimal places: BTC has no more than that on the blockchain, because one sat is the smallest unit there.^[1]
• Check the preview before sending: Enter amounts in the unit you’re currently looking at, and check the amount and unit before you confirm. A Bitcoin payment can’t be reversed.
• Not every price is the same: Every app shows a slightly different price, often with a mark-up. So compare how many sats you actually end up with.

‘Stack sats’: thinking in sats

In the Bitcoin community, regularly buying small amounts is called stacking satsGlossaryStack satsCommunity slang for regularly accumulating small amounts of bitcoin, counted in satoshis (sats) – usually via a savings plan and regardless of the price. 1 BTC is 100 million sats.On the learning path: Stage 4 · Step 4 – Setting up a savings plan →In the glossary →×, for example with a savings planGlossarySavings plan (Bitcoin savings plan)Automatically buying bitcoin at fixed intervals with a fixed amount, for example $50 a month. A savings plan takes the question of the right moment off your hands, but doesn’t promise a higher return.On the learning path: Stage 4 · Step 4 – Setting up a savings plan →In the glossary →×. Many people find it helpful to count in sats: the number grows with every purchase, whatever the price is doing. $25 a month for a year would come to 375,000 sats at a constant $80,000 and without fees; because the price fluctuates, in reality you get more or fewer each month. The DCA calculator works it through with real historical prices.