Bitcoin difficulty: the 2,016-block thermostat
Bitcoin retargets difficulty every 2,016 blocks to hold the ~10-minute pace. That feedback loop is why a fixed hashrate does not buy a fixed income — and why every yield estimate is a snapshot, not a promise.
Target, difficulty, epoch
Mining means finding a block-header hash below a target. A lower target = rarer hashes = higher 'difficulty' (a human-friendly ratio against Bitcoin's original target). Difficulty is not a count of miners and not an electricity meter — just the current bar.
Every 2,016 blocks (one epoch, nominally two weeks) the protocol compares actual elapsed time to the 10-minute target and rescales difficulty for the next epoch. Blocks came fast? The bar rises. Half the hashrate vanished? It falls. The adjustment is rule-based — it happens at block height, not on a wall-clock appointment, so the date of the next retarget is always an estimate.
Why your BTC/day is not fixed
Your expected share of rewards is roughly *your hashrate ÷ network hashrate*. Your machine's hashrate is fixed; the network's is not. If competitors add machines and difficulty rises 25%, your same rig expects 20% fewer coins per day — before price, fees, or tariff changes.
Other chains do it differently
The 2,016-block epoch is Bitcoin's design. Small chains usually retarget faster or continuously (SOQ retargets every block; MDS uses ASERT per-block; PRL targets a smooth curve) — same feedback idea, different damping. The general lesson transfers: hash-rate share decays as networks grow.
See it live on pow.family
Project analytics sections chart network hashrate over time — you can watch the growth that erodes fixed-rig yields on every coin we track.