Bitcoin’s fixed supply has emerged as one of its most compelling yet contentious features. The protocol has a strict limit of approximately 21 million coins, a cap that has profoundly influenced Bitcoin’s economic structure, cultural significance, and its positioning as “digital gold.”
While the last satoshi is expected to be mined around the year 2140, the ramifications of this supply cap are becoming increasingly apparent as the network nears its saturation point. By late 2025, over 95 percent of all bitcoins will have been mined, and with block rewards halving approximately every four years, the cryptocurrency landscape is steadily transitioning toward a time when transaction fees—rather than newly minted bitcoins—become essential for miner revenue.
We set out to explore the implications of a world where all bitcoins have been mined.
Key Takeaways
- Bitcoin is fast approaching its 21 million supply cap, with a significant number of coins already lost.
- Post-2140, miners will only earn from transaction fees, leading to a reevaluation of Bitcoin’s economic incentives.
- Network security will increasingly depend on robust fee markets; the absence of block rewards could weaken miner motivation.
- The fixed supply enhances Bitcoin’s status as “digital gold,” but it could limit its effectiveness as a daily currency.
Current Bitcoin Supply
As of November 2025, approximately 19.9 million bitcoins have been mined, representing over 95% of the total cap of 21 million.
The accompanying chart illustrates how the cumulative supply curve has flattened due to halving events that decrease new issuance. Currently, each new block generates only 3.125 BTC, compared to the original 50 BTC at launch.
In practical terms, this nearing cap has already curbed inflation: the current annual issuance rate falls below 2%. It’s important to note that a substantial portion of these bitcoins is effectively out of circulation—estimates indicate that roughly 20% of mined BTC (around 2–4 million coins) are permanently “lost” in inactive wallets as of 2020. This includes early coins for which the private keys have been forgotten or have remained untouched for many years. Consequently, the actual circulating supply is less than the total mined figure.
The 21-Million Cap and Rounding Effects
The Bitcoin protocol enforces a maximum supply of 21,000,000 BTC. However, due to the methodology used for rewards calculation in satoshis and the rounding down at each halving, the final total is expected to fall slightly below this figure. Specifically, because Bitcoin’s code uses binary shifts for reward halving, any fractional satoshis are discarded. Therefore, the ultimate supply will likely be in the vicinity of 20,999,999 BTC rather than an exact 21 million.
This technical nuance ensures that Bitcoin will never actually “mint” the last satoshi, but the difference is minimal compared to the overall supply. It is essential to recognize that even considering the theoretical cap, no new coins will be produced after the final satoshi is mined around 2140, marking the permanent cessation of block subsidies.
Miners and Network Security After the Cap
Upon the completion of the last subsidy, miners will transition to earning exclusively through transaction fees. While mining will persist, the financial viability of miners will hinge on the fees that users attach to their transactions for them to be processed. This shift carries profound implications for the ecosystem. Initially, miners may increase fees to accommodate their operational costs (e.g., electricity, hardware), as these fees become their sole income source.
Looking ahead, one can anticipate average transaction fees rising if demand remains robust since miners will compete based solely on fee quantities. However, it’s crucial to note that depending exclusively on fees could pose a risk to network security. Research conducted by Princeton University has indicated that sustaining a mining ecosystem through fees alone could catalyze destabilizing behaviors among miners.
For instance, given the irregular and volatile nature of fee rewards, miners might resort to tactics like “forking” or withholding blocks altogether (known as selfish mining or undercutting attacks) to optimize their fee earnings. Such tactics could waste hashing power and lead to delays in block confirmations, thereby undermining the overall security of the Bitcoin network. As a result, experts caution that the Bitcoin community may need to revisit its incentive structures or explore scalability solutions to ensure a smooth transition.
Economic Model: Fees, Deflation, and Store-of-Value
With no additional supply post-21 million, Bitcoin’s monetary framework will become purely disinflationary—and potentially deflationary if demand plateaus. This carries dual implications. On the one hand, the inherent scarcity is vital to Bitcoin’s value proposition. Many investors perceive Bitcoin as a variant of digital gold, holding it long-term as a safeguard against inflation in fiat currencies.
Conversely, chronic deflation could deter spending and complicate macroeconomic policies. As noted by Ernst & Young’s Paul Brody, if Bitcoin were to take on a significant role within a monetary framework, its rigid cap might necessitate reevaluation, as “many economists find that deflationary systems may not be optimal.” This issue remains mainly theoretical as we consider the horizon of 2140; by then, few other currencies—outside of gold—will maintain a fixed supply. However, it underscores a fundamental tension: Bitcoin’s capped model benefits early adopters disproportionately, while future users derive their value largely from the wealth created in the past.
At the same time, transaction fees will evolve into a cornerstone of Bitcoin’s economy. In a mature ecosystem, daily activity and fees might stabilize as part of a market mechanism. For instance, should most transactions migrate off-chain to quicker networks, on-chain fees could primarily be reserved for high-value payments or settlement purposes. In such a scenario, miners could still achieve profitability by charging elevated aggregate fees, provided they can process sizeable batches of transactions efficiently. However, if fees stagnate and mining becomes unfeasible, some miners might withdraw from the market or consolidate their operations. Overall, the network and economic landscape are expected to adjust to these impending changes rather than face outright failure.
The Bottom Line
Bitcoin’s protocol guarantees the total supply will remain below 21 million coins, a fundamental restriction that will transform the network’s economic framework. When the final bitcoins are mined around 2140, miners will rely solely on transaction fees.
In principle, this transition should not lead to system collapse—blocks will still be produced and coins will continue to circulate—but it will significantly alter Bitcoin’s economic landscape. In practice, miners’ compensation will hinge on fees (which might increase), network security will depend on these fees being adequate to deter malicious behavior, and the network could become less fluid as long-term retainers come to dominate. While the ecosystem is anticipated to adapt (through fee markets and new technical innovations), analysts concur that the fixed supply cap will inevitably present unique challenges for miners, along with new risks for investors as transaction incentives evolve.
