Chapter · Master Bitcoin
Supply cap and halvings
Bitcoin's rules cap the total supply at 21 million coins, and no one can change that without agreement from the whole network. New coins enter through the block reward, but that reward is cut in half roughly every four years in an event called the halving. Each halving slows the flow of new coins, and around the year 2140 the last tiny fraction will be mined. This built-in scarcity is central to Bitcoin's design.
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What you get asked
What is the maximum number of bitcoin that will ever exist, in millions?
The cap is fixed at 21 million coins. It is written into the rules that every node enforces, and it cannot quietly be raised.
About every four years the block reward is cut in half in an event called the ___.
The halving cuts new coin issuance in half. It happens every 210,000 blocks, which works out to roughly four years.
Order the block reward across Bitcoin's history
Each halving cuts the reward in half. The pattern of 50, 25, 12.5, 6.25, and 3.125 shows the steady slowdown of new supply.
What does each halving do to the supply of new coins?
A halving only affects newly issued coins, cutting them in half. Coins you already hold are never touched.
How does the network keep blocks near ten minutes as miners come and go?
Every 2,016 blocks, roughly two weeks, the network recalculates difficulty. More miners make the puzzle harder, fewer make it easier, keeping blocks near ten minutes.
The rest of this chapter
Learn what Bitcoin is, how it works, and how ordinary people buy, hold, and secure it safely.