Bitcoin's Controlled Supply

The precise issuance plan approaching 21 million. Supply schedule, lost coins, and the final coin in 2140.

3 min readLast updated: August 15, 2026

Key points

Bitcoin's true maximum supply is 20,999,999.9769 BTC, reached through 33 halvings every 210,000 blocks until new issuance stops entirely around 2140. As of March 2026, about 20 million BTC (roughly 95.2% of the cap) have been mined; the article also covers lost coins that shrink the effective supply and the debated shift to a fee-only economy once rewards end.

Total Supply: Why Not Exactly 21 Million?

Bitcoin's maximum supply is widely known as "21 million BTC," but the precise figure is 20,999,999.9769 BTC. This is due to the integer storage type used in the blockchain's transaction outputs—the final block rewards never perfectly sum to exactly 21 million.
The smallest unit of Bitcoin is 1 satoshi (0.00000001 BTC). Expressed in satoshis, the maximum supply is 2,099,999,997,690,000—approximately 2.1 quadrillion usable units.
The number "21,000,000" derives from 210,000 blocks × initial reward of 50 BTC × the geometric series sum (Σ 1/2^n). This mathematical elegance reflects Satoshi Nakamoto's design philosophy.

Reward Schedule: 33 Halvings

The block reward halves every 210,000 blocks (approximately 4 years). After a total of 33 halvings, the block reward reaches 0 satoshis.
Era 1 (Blocks 0–209,999): 50 BTC/block → Total: 10,500,000 BTC
Era 2 (Blocks 210,000–419,999): 25 BTC/block → Total: 5,250,000 BTC
Era 3 (Blocks 420,000–629,999): 12.5 BTC/block → Total: 2,625,000 BTC
Era 4 (Blocks 630,000–839,999): 6.25 BTC/block → Total: 1,312,500 BTC
Era 5 (Blocks 840,000–1,049,999): 3.125 BTC/block → Total: 656,250 BTC ← Current era
At block 6,930,000 (Era 34, around 2140), the reward drops to 0, and no new bitcoins will ever be created.

Supply Milestones

2009: ~2.62 million BTC (first year's issuance)
2012 (1st halving): ~10.5 million BTC (50% of total)
2016 (2nd halving): ~15.75 million BTC (75% of total)
2020 (3rd halving): ~18.375 million BTC (87.5% of total)
2024 (4th halving): ~19.6875 million BTC (93.75% of total)
March 2026: ~20 million BTC (~95.2% of total) ← Current
2028 (5th halving, projected): ~20.34 million BTC (96.875% of total)
~2140: 20,999,999.9769 BTC (final value)
If mining power had remained constant since the first Bitcoin was mined, the last Bitcoin would be mined around October 8, 2140.

Lost Coins: The Effective Supply

The theoretical maximum supply differs from the actual spendable supply. Many bitcoins have been permanently lost.
Genesis Block: The first 50 BTC cannot be spent due to a technical constraint in the protocol. Whether Satoshi designed this intentionally or it's a code quirk remains debated.
Block 124,724: A miner claimed 1 satoshi less than the full reward. That satoshi is permanently lost.
Block 501,726: 12.5 BTC were destroyed through an improper implementation.
Blocks 91,722/91,880 and 91,812/91,842: Duplicate transaction IDs rendered 100 BTC unspendable.
Beyond these technical losses, wallets with lost private keys and coins sent to provably unspendable addresses bring the estimated permanently lost total to 3–4 million BTC.

After 2140: Transition to a Fee Economy

After the last bitcoin is mined, miners' income will shift entirely from block rewards to transaction fees.
Satoshi Nakamoto wrote: "Once inflation goes to zero, miners will obtain an income only from transaction fees, which will provide an incentive to keep mining to make transactions irreversible."
Whether this transition proceeds smoothly is a critical question for Bitcoin's long-term security. The key factor is whether transaction volume and fees reach a sufficient level.
If Layer 2 solutions like the Lightning Network become widespread, on-chain transaction counts may decrease, potentially affecting fee revenue. This concern is actively debated as the "security budget problem."

Divisibility and Deflationary Design

Bitcoin is divisible to 8 decimal places. 1 BTC = 100,000,000 satoshis. This means even as coins are lost, the remaining supply can be subdivided to maintain circulation.
In the future, protocol upgrades could allow even smaller units. The Lightning Network already uses millisatoshis (1/1000 of a satoshi).
Coin loss effectively acts as "value appreciation" for existing holders. As the supply decreases, the relative value of each remaining coin increases.
This property is often compared to gold, but Bitcoin's supply schedule is far more precise and predictable than gold's.

Bitcoin's Controlled Supply

Total Supply: Why Not Exactly 21 Million?

Reward Schedule: 33 Halvings

Supply Milestones

Lost Coins: The Effective Supply

After 2140: Transition to a Fee Economy

Divisibility and Deflationary Design

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