Encyclopedia How the network works · Entry 222
Why Bitcoin blocks sometimes take an hour
In this article
At a glance
Key facts
A random search does not run on a timetable
Each candidate hash either meets the target or does not. Under the idealized independent-attempt model, there is no accumulated progress meter that forces a success when ten minutes have elapsed.
Difficulty controls the success threshold. Changing effective hash rate changes the rate of successful attempts until difficulty responds; the simple ten-minute model is an assumption for explanation, not a live measurement.
A thirty-minute gap is unusual but possible
Assuming a constant average interval of ten minutes, the probability of no block during a specified 30-minute period is exp(−30/10), about 4.98%. For a specified 60-minute period it is exp(−6), about 0.248%. These are model calculations, not forecasts for a particular day.
The probability refers to each stated observation window. It is not the probability that a whole day contains no long gap, which asks a different question.
Block arrival and your transaction’s inclusion are separate
Even when a block arrives, it may not contain a particular transaction. Miners select transactions and must respect validity and dependency requirements. Fees and local policy can affect which pending transactions they choose.
A wallet’s confirmation estimate therefore combines uncertainty about block timing with uncertainty about inclusion. A long wait does not alone prove a lost payment or a stopped network.
Direct answers
Questions people ask
After twenty minutes without a block, is one due in the next few seconds?
Not under the constant-rate independent-search model. The future waiting time does not shorten merely because the previous interval was unsuccessful. Actual changes in hash rate can change the model’s rate.
Does one confirmation always take ten minutes?
No. Ten minutes is an average target for blocks, and a transaction is not guaranteed inclusion in the next one. Actual confirmation time can be much shorter or longer.
Inspect the evidence
The answer and key facts have stable claim links. These records retain the scope and qualification when reused.
Bitcoin’s ten-minute target is an average, not a schedule for individual blocks. Miners repeatedly test candidate hashes, and successful attempts arrive irregularly. Under a stable-rate model, the waiting time is approximately exponential: a long gap is possible, and an unsuccessful wait does not make the next block due. Actual conditions can change when hash rate changes or difficulty adjusts.
Educational explanation. Product-specific behavior is scoped to the cited documentation, checked 2026-10-02.
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimTarget: About ten minutes per block on average
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimIndividual gap: Can be much shorter or longer
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimModel condition: A fixed effective block-finding rate
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimRevision history
- — First publication after primary-source research and separate automated verification.
Source register
Sources and references
Retrieval dates and locators are recorded individually.- Some things you need to knowBitcoin.org
Payment reversibility, confirmation risk and visible transaction records.
Locator: Bitcoin payments are irreversible; Unconfirmed transactions aren't secure; You are your own bank; Bitcoin is not anonymous · Retrieved: 2026-10-02T18:53:53.609ZOpen source - Block ChainBitcoin developer documentation
Chain validation, block timing, proof of work and accepted-chain context.
Locator: Block Height And Forking; Transaction Data; Proof Of Work; Consensus Rule Changes · Version / scope: Developer guide; historical implementation details require qualification · Retrieved: 2026-10-02T18:53:53.957ZOpen source - Bitcoin: A Peer-to-Peer Electronic Cash SystemSatoshi Nakamoto
Independent hash attempts, incentives, transaction collaboration limits and Poisson block-arrival approximation.
Locator: Sections 4, 6, 7, 10 and 11 · Version / scope: 2008 paper · Retrieved: 2026-10-02T18:53:58.187ZOpen source - MiningBitcoin developer documentation
Hardware work, candidate blocks and pool shares; historical examples are not current equipment recommendations.
Locator: Mining; Solo Mining; Pool Mining; Block Prototypes · Version / scope: Developer guide; historical implementation details require qualification · Retrieved: 2026-10-02T18:53:53.955ZOpen source - Payment ProcessingBitcoin developer documentation
Payment request interpretation, confirmation checks and refund destination risks; historical protocol sections are dated.
Locator: Requesting Payments; Verifying Payment; Issuing Refunds · Version / scope: Developer guide; historical implementation details require qualification · Retrieved: 2026-10-02T18:53:53.958ZOpen source
Research and drafting use AI assistance. A separate automated review checks claims against primary sources; no external expert or named human review is implied. Publication, substantive editing, source retrieval and verification are recorded separately. This version was independently checked by an automated reviewer on 2 October 2026.
Editorial method and correctionsDegrees of Satoshi editorial project. “Why Bitcoin blocks sometimes take an hour.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/bitcoin-block-time-variance/