Bitcoin hash rate explained: what it measures and why it changes

Every few minutes, somewhere in the world, a machine finds the hash that lets a new Bitcoin block be added to the chain. Hash rate is the number of attempts all the machines are making each second to get there.

The figure shows up in charts and headlines, usually with very large prefixes. Here’s what it counts, how it’s worked out when no one can measure it directly, what the units mean, why it moves, and what it can and can’t tell you. This article doesn’t quote current figures, because they change every day.

What hash rate counts

A hash is one run of Bitcoin’s hashing calculation. The Bitcoin Wiki defines “hash per second” as the number of double SHA-256 computations performed in one second, and calls the total across all miners the hash rate. In mining, each attempt means changing a number in the block header and hashing it again to see whether the result is below the target, as described in the previous article on how mining works.

The same word is used at two levels. For a single machine, hash rate is the main measure of its performance. For the network, it’s the combined attempts of every miner at once.

How the network’s hash rate is estimated

Nobody can count the network’s attempts directly. The Bitcoin Wiki explains that because each miner or pool only relays a solved block to the network, the overall hash rate is calculated from the time between blocks. Bitcoin Core’s own command works the same way, returning the estimated network hashes per second based on the last n blocks, 120 by default.

The estimate relies on the link with difficulty. Difficulty is set so that blocks arrive about every 10 minutes, so the Bitcoin Wiki gives a rule of thumb that network hash rate is roughly the difficulty multiplied by 2 to the power of 32 and divided by 600, the number of seconds in ten minutes. Blocks arrive at random, though, so a short window can swing either way. The wiki cautions that such figures are not accurate at any given instant, while measurements over longer periods are indicative.

The units, from H/s to EH/s

Hash rate is written in hashes per second, with standard metric prefixes where each step is a thousand times the last: kilo, mega, giga, tera, peta, and exa. A single mining machine is usually quoted in terahashes per second, while the whole network is quoted in exahashes per second. One exahash per second is 10 to the power of 18, or a quintillion, hashes every second.

The Bitcoin Wiki gives a sense of the growth. In January 2015 the network ran at around 300 petahashes per second, and by April 2021 it was around 170,000. At the lowest difficulty, the wiki notes, the rule of thumb works out to about 7 million hashes per second.

Why hash rate changes

Hash rate goes up when more machines come online or faster hardware replaces older equipment, and it goes down when machines are switched off. As the Bitcoin white paper puts it, mining spends CPU time and electricity, so costs and conditions affect which machines keep running.

The difficulty adjustment adds a delay. Difficulty is recalculated about every two weeks, or every 2,016 blocks, so a change in hash rate shows up first as blocks arriving faster or slower than ten minutes, and only later in the difficulty. The randomness of block times also makes the estimated figure move even when nothing has changed.

What hash rate does and doesn’t tell you

Hash rate shows how much computing effort is being spent competing for blocks. It also relates to security, because the white paper explains that history is hard to rewrite as long as honest nodes control the majority of the computing power, so a larger total generally means an attacker needs more.

It doesn’t tell you where the bitcoin price is going, whether mining is profitable for anyone in particular, or how quickly transactions are processed. For an individual miner, what matters is their share of the total, because the chance of finding the next block depends on how their hash rate compares with the network’s.

WEEX Reminder: charts are estimates, not signals

WEEX reminds users that hash rate figures are estimates, and that they don’t predict prices or returns. Be careful with promotions that use “mining power” numbers to justify promised returns, since no one can guarantee profits from mining. Never share a seed phrase or verification code with anyone offering to “mine” for you. Nothing here is financial advice.

Conclusion

Bitcoin’s hash rate is the number of hashing attempts miners make each second, and because it can’t be measured directly, it’s estimated from how fast blocks arrive and the current difficulty. It’s quoted in prefixes up to exahashes per second, it moves with the hardware and costs miners face, and the difficulty adjustment follows it with a delay. It describes mining activity and security effort, not price.

FAQ

1. What is Bitcoin hash rate?
It’s the number of hashing attempts miners make per second as they compete to find the next block. It can describe a single machine or the whole network.

2. How is Bitcoin’s hash rate measured?
It isn’t measured directly. It’s estimated from the time between blocks and the current difficulty, as Bitcoin Core’s network hash rate command does over the last 120 blocks by default.

3. What does EH/s mean?
It stands for exahashes per second. One exahash per second is 10 to the power of 18 hashes every second, a quintillion.

4. Why does hash rate go up and down?
Machines come online or go offline, hardware improves, costs change, and the difficulty adjusts only about every two weeks. The estimate also moves because blocks arrive at random.

5. Does a higher hash rate mean a higher bitcoin price?
No. Hash rate describes mining activity, not price direction, and it isn’t a trading signal.