Mining and
proof of work.

The lottery analogy

Think of mining as a raffle that runs continuously. Each time a miner computes a hash, it is buying one ticket. The more hashes per second a miner can compute, the more tickets it holds. The network draws a winning ticket roughly every ten minutes.

If you control one percent of the global hash rateHash rateHow many hashes (guesses at the puzzle that wins a block) a miner makes per second. The network hash rate is the total across all miners: the higher it is, the harder and more expensive it would be for any attacker to overpower the network.Full definition, you will find roughly one percent of the blocks over time. Expected time between your blocks is the block interval (ten minutes) divided by your share. At one percent, that is about every sixteen hours. At 0.001 percent, it is about every two years on average, with enormous variance.

There is no partial credit. Miners either find the block or they do not. This is why small miners join pools that split rewards proportionally to contributed work, or solo-mine and accept long odds of a large payout.

SHA-256 and the target

Every block header is fed through SHA-256Secure Hash Algorithm 256-bit (SHA-256)The cryptographic function Bitcoin uses to convert any data into a fixed-length code, used in mining and transaction verification.Full definition twice. The output is a 256-bit number. For the block to be valid, that number must be lower than a target value set by the protocol. The target looks like a long string of leading zeros in hex.

Miners cannot choose the output of SHA-256. They can only change one small field in the header (the nonce, plus a few other tweaks) and try again. Hash, check, increment, hash, check, increment. A modern ASIC can do this hundreds of trillions of times per second.

Difficulty adjustment

Every 2,016 blocks (roughly every two weeks at ten-minute intervals) the network adjusts the target based on how fast the previous 2,016 blocks were mined. If they came in faster than two weeks, the target tightens (difficulty goes up). If they came in slower, the target loosens (difficulty goes down).

This is the mechanism that keeps block time at roughly ten minutes regardless of how much global hash rate joins or leaves. When China banned mining in mid-2021, global hash rate fell roughly 50 percent in weeks. Blocks slowed to fifteen to twenty minutes. At the next adjustment, difficulty dropped, and block time returned to ten minutes on a smaller network. Six months later, when miners had relocated and rebuilt capacity, hash rate was at new all-time highs and difficulty had climbed to match.

Block reward and the halving schedule

Each block pays its miner two things: a newly-minted "coinbase" reward and the fees attached to the transactions included in the block. The coinbase started at 50 BTC per block in 2009 and halves every 210,000 blocks (roughly every four years).

After the April 2024 halvingHalvingThe scheduled event, built into Bitcoin's code, that cuts the new bitcoin paid to miners per block in half. It happens every 210,000 blocks, about every four years; the April 2024 halving at block 840,000 cut it from 6.25 to 3.125 BTC, slowing the rate of new supply.Full definition the reward is 3.125 BTC per block. At a Bitcoin price around $80,000, that is roughly $250,000 of new issuance per block plus a few thousand dollars in fees, paid every ten minutes to whichever miner wins. See The Bitcoin Halving for the full schedule.

Network hash rate in 2026

Network hash rate is the total number of SHA-256 hashes the entire network computes per second, summed across every machine. In the week to September 24, 2026 it averaged about 926 EH/s. That is 926 exahashes per second, which is 926 quintillion hashes every second.

Why mining secures Bitcoin

Full nodes independently validate blocks and transactions, then select the valid chain with the greatest cumulative proof of work, not the largest miner headcount or the most blocks. Majority hashpower cannot make a node accept invalid signatures or invalid issuance under its existing rules. It can enable censorship, reorganizations and double-spends of the attacker’s own payments; it cannot sign for someone else’s keys. Security is probabilistic and depends on honest hashpower, network communication and correct validation. More confirmations reduce, but do not eliminate, reversal risk.^[1]

Proof of work makes competing histories costly, while full-node validation enforces the rules. Energy expenditure is not authority to create an otherwise invalid block.^[1]