Bitcoin produces a block roughly every ten minutes whether a thousand machines are mining or a hundred million. The mechanism that makes that possible is difficulty — and it quietly controls your revenue.
Every 2,016 blocks — about two weeks — the Bitcoin protocol compares how long those blocks actually took against the 10-minute target. Came in fast? More hashrate joined; difficulty ratchets up proportionally. Too slow? Hashrate left; difficulty drops. The result is a self-regulating system that has held block times near ten minutes for fifteen years across a million-fold change in network power.
Your machine's share of network rewards equals your hashrate divided by total network hashrate — and difficulty is the proxy for that denominator. When difficulty rises 5%, every machine on earth earns ~5% less BTC per day, immediately. This is the number that erodes mining revenue between halvings, and any honest profitability forecast must assume it keeps growing. Plugging today's difficulty into a 24-month projection and holding it flat is the most common — and most expensive — modeling mistake new miners make.
Professional miners model difficulty growth scenarios — flat, moderate (~2–4% per adjustment period annualized trend), aggressive — and check breakeven under each. Our free mining calculator pulls live network difficulty so your projections start from reality. And the structural defense against difficulty growth never changes: the most efficient machines you can buy, on the cheapest power you can find.