Block Height
Block height is a block's ordinal number counted from the very first one. The network lives by this counter: halvings, rule activations, and schedules are tied to height, not to dates.
What block height is
The first block of a network is called the genesis, and its height is zero. Every next block adds one, so the current height is the length of the chain. When someone says at height 840000, they mean a specific moment in the network's history that cannot be confused with anything else.
Height beats dates because blocks arrive unevenly: on Bitcoin once every ten minutes on average, yet a bit more often today and less often tomorrow. An event scheduled for a height happens strictly by network rules, while its date can only be estimated.
The big events are measured exactly this way. The Bitcoin halving hits every 210000 blocks, the difficulty adjustment every 2016. New rule activations get pinned to a height too, so every node switches at the same block instead of the same hour.
For a miner, height is also a working coordinate: the pool states it in jobs, an explorer finds any block by it, and arguments about when the halving happened are settled with a single number instead of time zones.
The short version in a table
| Counting starts | at the genesis, which sits at height zero |
| What it shows | chain length and a moment in history |
| Bitcoin halving | every 210000 blocks |
| Difficulty adjustment | every 2016 blocks |
| Why not dates | blocks arrive unevenly, height is exact |
Where height comes in handy for you
Count down to the halving: subtract the current height from the nearest multiple of 210000 and multiply by ten minutes. More accurate than any calendar.
Look up your block or payout in an explorer by height: it is shorter and less ambiguous than a hash.
Read network news correctly: activation at height X means a rule that switches on at a specific block across the whole network at once.
Check your node when solo mining: your height lagging behind the explorer means the node is still catching up and it is too early to mine.
A counting example
Bitcoin halvings landed at heights 210000, 420000, 630000 and 840000: the schedule reads like a multiplication table. The dates of those events were known in advance only roughly, the heights exactly: the network runs a calendar in blocks, and nothing can run late by it.
Related terms
Where to go next on the site
Coins
Numbers
Questions and answers
Can the height decrease
On a node, briefly yes: during a fork the other branch wins and the last block gets replaced. Deep rollbacks do not happen on large networks.
Two networks share the same height, is that a coincidence
Yes, the counters are independent: each network has its own genesis and its own block pace. Comparing heights across networks is pointless.
How do I find the current height
In any block explorer or on your own node. The pool also shows the height it is currently building a block at.
How the terms connect
Every link in the chain is clickable. Orange marks where you are now.
Looking for an ASIC miner
The catalog holds 212 models. You can compare them by hashrate and by joules per terahash, then plug your own rate into the calculator and see what stays in your pocket.
Page written and checked by Denys Klimchuk. Updated .