Bitcoin hashrate explainedWhat is the hashrate of bitcoin?

The hashrate is how many computing attempts the Bitcoin network makes per second to find a new block. The higher the hashrate, the more computing power sits behind Bitcoin. And the more computing power, the safer the network is.

You sometimes hear other terms for the same thing: computing power, computer power, hashing power or hashing speed. In this article we keep it simple and mainly use the word hashrate.

The word comes from two parts. "Hash" is a kind of mathematical blender that miners run numbers through. "Rate" means speed. Together: how fast can the network hash?

Bitcoins are "mined". That sounds complicated, but it comes down to guessing very fast. Miners are specialised computers that keep running three things through a SHA-256 hash function:

• A piece of data from the block most recently added to the blockchain.
• A new block with pending transactions.
• A random number, the "nonce".

The outcome is a hash. That hash has to fall below a certain threshold that the network sets itself (the "difficulty target"). Does it not work? Then the miner tries another nonce. And another. And another. Millions of times per second.

The hashrate is precisely that: the total number of attempts per second by all miners together. Whoever finds the right hash first gets to add the block to the chain and receives new bitcoins as a reward.

A higher hashrate means: more computers are working on the network. And that makes Bitcoin safer.

Anyone who wants to hijack the network has to get hold of 51% of all computing power. That is called a 51% attack. The higher the hashrate, the more hardware and electricity you need for it. In practice that bill became astronomical long ago.

That is why the hashrate is also a handy health meter. Is it rising? Then miners trust the network enough to invest in new equipment. Is it falling sharply? Then miners are pulling out, for example because electricity has become too expensive or because a country has banned mining.

One caveat: it is not only the number that counts, but also the spread. If a great deal of hashrate sits in one country, that is more vulnerable than when it is spread around the world.

The basic unit is hashes per second, abbreviated as H/s. But because the Bitcoin network is gigantic, in practice you use larger units:

At the time this article was written, the Bitcoin network worldwide does a few hundred EH/s together. That is hundreds of quintillions of attempts per second, an unimaginably large number.

To deliver that computing power, miners use ASICs: chips built specifically for Bitcoin. A common ASIC costs a few thousand euros and is thousands of times faster than an ordinary laptop.

Bitcoin is programmed to produce a block every 10 minutes on average. No more, no less. But the hashrate changes constantly: new miners join, old ones drop out. So how does the network keep to that 10-minute rhythm?

The answer: the difficulty (mining difficulty). Every 2,016 blocks, roughly two weeks, the network looks at how fast those blocks were found:

• Faster than 10 minutes on average? The difficulty goes up.
• Slower than 10 minutes on average? The difficulty goes down.

That keeps the pace predictable, even if the hashrate grows or shrinks considerably. It is one of the most elegant pieces of Satoshi design.