Bitcoin's Total Supply: The 21 Million Cap
Bitcoin has a fixed maximum supply of exactly 21 million coins. This hard cap is one of Bitcoin's most important features and is enforced by the protocol's consensus rules. Unlike traditional fiat currencies, which central banks can print at will, Bitcoin's supply is mathematically predetermined and cannot be changed.
Why 21 Million?
The 21 million limit was chosen by Satoshi Nakamoto, Bitcoin's anonymous creator. While the exact reasoning was never explicitly stated, the number emerges from Bitcoin's emission schedule:
- Initial block reward: 50 BTC per block
- Halving interval: Every 210,000 blocks (~4 years)
- Mathematical result: 210,000 × 50 × 2 = 21,000,000 BTC
This geometric series (50 + 25 + 12.5 + 6.25 + ...) converges to 21 million, creating a supply curve that mimics the extraction of precious metals like gold—hence Bitcoin's nickname as "digital gold."
The Code Behind the Cap
Bitcoin's supply limit is enforced in the source code. Every full node on the network validates that no more than 21 million Bitcoin can ever exist. Any attempt to create additional coins would result in the transaction or block being rejected by the network.
// Bitcoin Core consensus rule
static const CAmount MAX_MONEY = 21000000 * COIN;
How Many Bitcoins Exist Today?
As of December 2024, approximately 19.5 million Bitcoins have been mined. This represents about 93% of the total supply that will ever exist. The remaining ~1.5 million BTC will be mined over the next 116 years, with the final Bitcoin expected to be mined around the year 2140.
Bitcoin Supply Timeline
| Year | Total Mined | % of Max | Block Reward |
|---|---|---|---|
| 2009 | ~1.6 million | 7.6% | 50 BTC |
| 2012 | 10.5 million | 50% | 50 → 25 BTC |
| 2016 | 15.75 million | 75% | 25 → 12.5 BTC |
| 2020 | 18.4 million | 87.5% | 12.5 → 6.25 BTC |
| 2024 | 19.5 million | 93% | 6.25 → 3.125 BTC |
| 2028 | ~20.3 million | 96.5% | 3.125 → 1.5625 BTC |
| 2140 | 21 million | 100% | 0 BTC |
Bitcoin Mining and Block Rewards
New Bitcoins enter circulation through a process called mining. Miners use specialized hardware to solve complex mathematical puzzles, and the first miner to solve each puzzle gets to add a new block to the blockchain and receives a reward in newly minted Bitcoin.
How Many Bitcoins Are Created Daily?
With the current block reward of 3.125 BTC (since April 2024) and approximately 144 blocks mined per day (one block every ~10 minutes), the daily Bitcoin creation rate is:
Block Reward Breakdown
- Per block: 3.125 BTC
- Per hour: ~18.75 BTC (6 blocks)
- Per day: ~450 BTC (144 blocks)
- Per week: ~3,150 BTC
- Per month: ~13,500 BTC
- Per year: ~164,250 BTC
The Role of Transaction Fees
In addition to the block reward, miners also receive transaction fees from users. As the block reward decreases over time, transaction fees will become the primary incentive for miners. By 2140, when all Bitcoin is mined, miners will rely entirely on fees.
The Bitcoin Halving Explained
Bitcoin halving is a programmed event that cuts the block reward in half approximately every four years (exactly every 210,000 blocks). This mechanism controls Bitcoin's inflation rate and ensures the 21 million cap is never exceeded.
Complete Halving History
| Halving | Date | Block Height | Reward Before | Reward After |
|---|---|---|---|---|
| Genesis | Jan 3, 2009 | 0 | - | 50 BTC |
| 1st Halving | Nov 28, 2012 | 210,000 | 50 BTC | 25 BTC |
| 2nd Halving | Jul 9, 2016 | 420,000 | 25 BTC | 12.5 BTC |
| 3rd Halving | May 11, 2020 | 630,000 | 12.5 BTC | 6.25 BTC |
| 4th Halving | Apr 20, 2024 | 840,000 | 6.25 BTC | 3.125 BTC |
| 5th Halving | ~2028 | 1,050,000 | 3.125 BTC | 1.5625 BTC |
Why Does Halving Matter?
- Controls Inflation: Each halving reduces Bitcoin's inflation rate by 50%
- Increases Scarcity: Fewer new coins means existing coins become more scarce
- Predictable Supply: Anyone can calculate exactly how many Bitcoin will exist at any future date
- Historical Price Impact: Previous halvings have preceded significant price increases
How Many Bitcoins Are Lost Forever?
One of Bitcoin's most fascinating aspects is that coins can be permanently lost. Unlike bank accounts that can be recovered, lost private keys mean those Bitcoins are gone forever—still visible on the blockchain but completely inaccessible.
Estimated Lost Bitcoin
Research by blockchain analytics firms like Chainalysis and Glassnode suggests that 3 to 4 million Bitcoin are permanently lost. This includes:
🗝️ Lost Private Keys
Early adopters who mined or bought Bitcoin didn't always securely store their keys. Hard drive crashes, forgotten passwords, and discarded computers have claimed millions of coins.
💀 Deceased Holders
Bitcoin holders who died without sharing their keys or including crypto in their estate planning leave their coins permanently inaccessible.
🗑️ Burn Addresses
Some Bitcoin have been sent to "burn addresses" with no known private keys, either accidentally or intentionally (for proof-of-burn protocols).
⚠️ Early Mining Bugs
Some early blocks had rewards sent to addresses with bugs in the scripts, making those coins unspendable. The genesis block's 50 BTC is also unspendable.
Famous Cases of Lost Bitcoin
- James Howells: Accidentally threw away a hard drive containing 8,000 BTC (worth billions today) in a Welsh landfill in 2013
- Stefan Thomas: Lost the password to a hardware wallet containing 7,002 BTC, with only 2 guesses remaining before it locks permanently
- Mt. Gox: While not truly "lost," 850,000 BTC were stolen/lost in the 2014 exchange hack, many of which may never be recovered
- QuadrigaCX: ~26,500 BTC allegedly lost when the exchange's founder died with sole access to the cold wallets
Actual Circulating Supply
The "circulating supply" of Bitcoin is a nuanced metric. While ~19.5 million BTC have been mined, not all of these are actively circulating in the economy.
Breaking Down the Supply
| Total Mined: | ~19,500,000 BTC |
| Minus Lost Coins: | -3,000,000 BTC |
| Minus Satoshi's Coins: | -1,100,000 BTC |
| Minus Long-term Holders: | -1,400,000 BTC |
| Estimated Active Supply: | ~14,000,000 BTC |
Dormant Bitcoin
Beyond permanently lost coins, millions of Bitcoin haven't moved in years. On-chain analysis reveals:
- ~30% of all Bitcoin hasn't moved in 5+ years
- ~12% hasn't moved in 10+ years
- ~6% has never moved since being mined (excluding known exchange addresses)
These dormant coins are often referred to as "HODLed" (held long-term) and represent investors with strong conviction who don't sell regardless of price.
Satoshi Nakamoto's Bitcoin
Satoshi Nakamoto, Bitcoin's pseudonymous creator, is estimated to have mined approximately 1.1 million Bitcoin in the network's early days. These coins have never moved and are identifiable through a unique mining pattern called the "Patoshi Pattern."
The Patoshi Pattern
Research by Sergio Demian Lerner identified that a single miner (believed to be Satoshi) mined approximately 22,000 blocks in Bitcoin's first year. This miner used a slightly different nonce pattern than other miners, leaving a distinct "fingerprint."
What If Satoshi's Coins Move?
The movement of Satoshi's coins would be the biggest event in Bitcoin's history. It would:
- Prove Satoshi (or someone with access to Satoshi's keys) is still alive and active
- Potentially create massive market volatility
- Raise questions about decentralization if such a large holder becomes active
Why Bitcoin's Scarcity Matters
Bitcoin's fixed supply of 21 million coins is fundamentally different from any traditional currency or asset. This mathematical scarcity has profound implications.
Stock-to-Flow Model
The Stock-to-Flow (S2F) ratio measures scarcity by dividing existing supply (stock) by annual production (flow). Bitcoin's S2F increases after each halving:
- 2012-2016: S2F ~25 (comparable to silver)
- 2016-2020: S2F ~50
- 2020-2024: S2F ~100 (surpassing gold's ~62)
- 2024+: S2F ~200+ (the most scarce asset on Earth)
Bitcoin vs. Traditional Assets
| Asset | Supply Limit | Annual Inflation |
|---|---|---|
| Bitcoin | 21 million (fixed) | ~0.85% (decreasing) |
| Gold | Unknown (estimated) | ~1.5% |
| US Dollar | Unlimited | Variable (historically 7%+) |
| Euro | Unlimited | Variable (historically 4%+) |
Implications of Fixed Supply
- No Inflation: Unlike fiat currencies, no central authority can "print" more Bitcoin
- Predictability: The supply schedule is known for the next 100+ years
- Store of Value: Scarcity is a key property of sound money (like gold)
- Increasing Scarcity: As coins are lost, the effective supply decreases over time
Frequently Asked Questions
How many Bitcoins are there in total?
The maximum supply of Bitcoin is capped at 21 million coins. As of late 2024, approximately 19.5 million Bitcoins have been mined, leaving about 1.5 million yet to be created through mining over the next ~116 years.
When will all 21 million Bitcoins be mined?
The last Bitcoin is expected to be mined around the year 2140. Due to the halving mechanism that reduces mining rewards every 210,000 blocks (approximately every 4 years), the rate of new Bitcoin creation decreases exponentially over time.
How many Bitcoins are lost forever?
Estimates suggest that between 3-4 million Bitcoins are lost forever due to lost private keys, forgotten wallets, and coins sent to unspendable addresses. This includes an estimated 1.1 million BTC held by Satoshi Nakamoto that have never moved.
What is Bitcoin halving?
Bitcoin halving is an event that occurs approximately every 4 years (every 210,000 blocks) where the block reward for miners is cut in half. Starting at 50 BTC in 2009, the reward is now 3.125 BTC after the April 2024 halving.
How many new Bitcoins are created daily?
With the current block reward of 3.125 BTC and approximately 144 blocks mined per day, around 450 new Bitcoins are created every day. This rate will halve again in 2028.
Why is Bitcoin's supply limited to 21 million?
Bitcoin's 21 million cap was chosen by Satoshi Nakamoto to create digital scarcity and prevent inflation. This fixed supply makes Bitcoin deflationary by design, unlike fiat currencies that can be printed indefinitely. The number emerges mathematically from the halving schedule: 210,000 blocks × 50 BTC × 2 = 21,000,000.
How many Bitcoins are in circulation?
While approximately 19.5 million Bitcoins have been mined, the actual circulating supply is lower. After accounting for lost coins (3-4 million), Satoshi's dormant coins (~1.1 million), and long-term holdings, an estimated 14-16 million Bitcoins are actively circulating.
Can the 21 million limit ever be changed?
Theoretically, Bitcoin's code could be modified to increase the supply limit, but this would require consensus from the vast majority of the network (miners, nodes, developers, and users). Such a change would fundamentally alter Bitcoin's value proposition and would likely result in a chain split, with the original 21 million-capped version continuing alongside any modified version. In practice, changing this limit is considered virtually impossible.
What happens when all Bitcoins are mined?
When all 21 million Bitcoins are mined (around 2140), miners will no longer receive block rewards. Instead, they will earn only from transaction fees. This transition is expected to be gradual, as block rewards will become negligible compared to fees long before reaching zero.