There will only ever be 21 million bitcoin. That number is fixed in Bitcoin's software, and every computer running the network checks it. As of now, most of those coins already exist, and the rest are released on a slow, published schedule that ends around the year 2140.
The part most first-time buyers miss: you don't need a whole coin. Each bitcoin splits into 100 million smaller units called satoshis, or 10 crore sats in the way we count in India. So a fixed supply doesn't lock anyone out. It means every rupee you put in buys a share of something nobody can print more of.
The short answer
21 million is the cap. Not "about" 21 million, not "for now". The exact ceiling works out to a hair under 21 million, 20,999,999.9769 BTC, because of how the software stores amounts. For every practical purpose, 21 million is the number.
I've been explaining this number to people in India since the Bitcoin meetups we ran in Bangalore in 2012 and 2013. The question used to be "who decides how many there are?" The answer still surprises people. Nobody decides. It was decided once, in the code, and the network has enforced it ever since.
Where the 21 million limit lives
Bitcoin has no head office that could change its mind. It runs on thousands of computers around the world that all follow the same rules. One of those rules says how many new coins each block can create. If a miner tries to pay themselves more than the rule allows, every other computer on the network rejects that block. It's thrown out like a fake note at a bank counter.
That's the important difference from money we're used to. The rupee, the dollar, any currency a central bank manages, can be issued in larger amounts when the people in charge decide it's needed. I'm not saying that's evil. I'm saying it's a decision, made by people. With Bitcoin, the supply isn't a decision anyone gets to make on a Tuesday.
If you've watched the price of milk, petrol, rent and school fees climb over your life, you already understand why that matters to people. A supply nobody can stretch is the whole idea.
How new bitcoin enters circulation
New coins come from mining. Roughly every ten minutes, a new block of transactions gets added to Bitcoin's public ledger. The miner who adds it earns a block reward, a set number of brand new bitcoin, plus the fees people paid to have their transactions included.
The Bitcoin whitepaper describes this as the incentive that keeps the network honest: miners spend real electricity and hardware to secure the ledger, and the reward is how they get paid for it. It's also the only way new bitcoin is created. There's no other tap.
When Bitcoin started in 2009, the reward was 50 BTC per block. It hasn't stayed there.
Halvings and the slow approach to the cap
Every 210,000 blocks, roughly every four years, the block reward is cut in half. This is called the halving. It has happened four times so far: in 2012, 2016, 2020, and most recently in April 2024, when the reward fell from 6.25 BTC to 3.125 BTC per block.
The next halving is expected in 2028, when the reward drops to 1.5625 BTC. The exact date depends on how fast blocks arrive, so you'll see estimates move around a bit as it gets closer.
Because the reward keeps halving, new supply shrinks each cycle. Most of the 21 million has already been mined, but the last fractions trickle out over more than a century. Estimates put the final satoshi around 2140. After that, miners earn only from transaction fees.
I find this the most elegant part of the design. Nobody has to announce a policy change. The schedule was public on day one, and anyone can check where we are on it by looking at the current block height.
What happens when all bitcoin are mined?
The network keeps running. Blocks still get added every ten minutes or so, transactions still need to be confirmed, and miners still need to be paid. The difference is that their income comes entirely from fees users pay, not from new coins. Block space is limited, so people bid for it, and that bidding is what pays for security in the long run.
Why a fixed supply does not mean you need a whole coin
This is where I spend most of my time when I talk to first-time buyers in India. They hear "21 million" and "one bitcoin costs lakhs of rupees" and they assume Bitcoin isn't for them.
It is. One bitcoin is 100 million satoshis. 10 crore sats. When you buy ₹10 of Bitcoin, you get a small number of satoshis, and they're yours in the same way a whole coin would be. The IndiaBitcoin home page shows exactly how many sats ₹10, ₹100 and ₹1,000 buy at the live price, so you don't have to do the maths yourself.
Think of gold. Very few families buy a whole kilo bar. They buy a coin, a chain, a few grams at Dhanteras. Nobody feels left out of gold because a kilo is expensive. Sats work the same way, except the smallest unit is far smaller than any gram.
When I first bought Bitcoin, one coin cost somewhere around $5 to $10, about 500 rupees. That era is gone. What hasn't changed is that you can start small and still own a real piece of a fixed supply.
Thinking in sats
One habit I recommend: stop asking "how much is one bitcoin?" and start asking "how many sats did my rupees buy?" The first question makes Bitcoin feel out of reach. The second makes it something you can learn with ₹10. On Unocoin you can buy from ₹10 through a Systematic Buying Plan, which is how a lot of people do their first purchase.
How to explain 21 million in one minute
At our early meetups, people would bring a friend who had never heard of Bitcoin, and someone would have to explain it on the spot. The short version I use today fits in three sentences.
There's a fixed number of coins, 21 million, and the software won't allow more. New coins come out on a schedule that gets slower every four years, until it stops. You can buy a tiny slice, down to one hundred-millionth of a coin, so the fixed number doesn't keep anyone out.
That's enough to start a good conversation. Everything else, wallets, fees, tax, comes after someone understands why the supply matters.
What 21 million does not tell you
A fixed supply doesn't fix the price. Bitcoin's price is set by what buyers and sellers agree on each day, and it can fall sharply as well as rise. I've lived through several of those falls from inside an exchange. Scarcity is a property of the supply. It isn't a promise about what your holding will be worth next month.
So learn the basics first. Understand the cap, understand halvings, understand sats. Then decide for yourself, with money you could hold through big swings. If tax is on your mind, the India crypto tax guide covers the 30% flat tax and 1% TDS in plain words. And check with a CA before you file.
If this is your first week learning about Bitcoin, the Learn page covers the basics, security and tax in one place.
Common questions
Can the 21 million limit be changed?
The supply schedule is written into Bitcoin's software and enforced by every computer that runs it. Changing it would need the people running the network to accept different rules, which is why the cap has held since 2009. Treat it as a rule the network enforces, not a promise from a company.
When will the last bitcoin be mined?
Estimates put it around the year 2140. The exact date depends on how fast blocks arrive in the future, so nobody can give you a day. After that, miners are paid from transaction fees only.
How many bitcoins are lost?
Nobody knows the exact number. Coins sent to a wallet whose keys are lost can never be moved again, so the number that can circulate is lower than the number mined. Any precise figure you see is an estimate.
Why is Bitcoin divisible?
Each bitcoin divides into 100 million satoshis, which in Indian numbering is 10 crore. That lets someone buy ₹10 of Bitcoin and own a real, countable piece of it.