Guide · Oct 19, 2026 · 5 min read
What a hash is, and what the TH/s on a miner's spec sheet counts
A hash is a fingerprint, and a miner is a machine that makes hundreds of trillions of them a second, looking for one that starts with enough zeros. Here is one real block's fingerprint, what it took to find, and what TH/s then tells you about a machine.
A hash is a fingerprint that changes completely if you touch the input
A hash function takes any piece of data and returns a short, fixed-length fingerprint of it. Bitcoin uses one called SHA-256, which always returns 64 characters of numbers and letters. Give it the word "Firsthand" and it returns c237964e7a72 and fifty-two more characters. Give it "firsthand", with a lowercase f, and it returns bbb18ca53968 and fifty-two more. Nothing about the first answer hints at the second.
Two things follow. The same input always gives the same fingerprint, so anyone can check it. And there is no way to work backwards from a fingerprint to an input that makes it. If you want a fingerprint with a particular look, the only method is to try inputs one after another until one has it. That trying is what a bitcoin miner is built to do.
There is no shortcut from a fingerprint back to the data, so the only way to find a special one is to try.
One real block's fingerprint starts with twenty zeros
Every bitcoin block has an 80-byte header: a version number, the fingerprint of the block before it, a summary of its transactions, a timestamp, the difficulty setting and one free number called the nonce. Mining means changing the nonce, hashing the header twice with SHA-256 and checking the result.
Block 971,712 was found at 12:37 UTC on 16 October 2026, the block at which difficulty reset, and its header is on the mempool.space block page. We hashed that header ourselves and got 00000000000000000000c185f0906690a08d62d6fe842682a888d5560217e467, exactly the fingerprint the network recorded. It has twenty zeros in front. The nonce that produced it was 3,894,702,701. Change that number by one and the fingerprint becomes 64 unrecognisable characters, almost certainly with nothing like twenty zeros.
The rule is that the fingerprint, read as a number, has to be below a target the network sets. A lower target means more zeros are needed in front, and difficulty is that target written as a plain figure. The difficulty guide covers how it is reset every two weeks.
Finding the fingerprint is hard, and checking it takes one step
The whole design rests on a lopsided effort. Producing a fingerprint with twenty zeros took the network about 6 × 10²³ guesses. Checking it takes a single hash: anyone, on any computer, can hash the header and see the zeros for themselves, which is exactly what we did above.
That lopsidedness is what the electricity buys. To rewrite a block, someone would have to redo all the guesses for it and for every block built on top of it, faster than the rest of the network keeps adding new ones. The miners' guesses are the cost of making the record expensive to change, and each machine is paid for the share it contributes.
It also explains the ten-minute rhythm. Difficulty is reset every 2,016 blocks so that, whatever the network's total guesses, a block still arrives about every ten minutes. More machines means a harder target to hit, and not faster blocks.
At today's difficulty a block takes about 600 sextillion guesses
Difficulty was set to 140.58 trillion at block 971,712. The average number of guesses needed to win a block at that setting is the difficulty multiplied by 4.29 billion, which is about 6.04 × 10²³, or 604 sextillion. The network wins a block about every ten minutes, so every second it is making around 10²¹ guesses. That is a zettahash a second, and difficulty implies about 1.0 of them today.
A hash is one guess, and hashrate is guesses per second. The units step up by a thousand each time, and the spec sheet and the network sit at opposite ends of the ladder.
| Unit | Guesses a second | Where you meet it |
|---|---|---|
| TH/s | 1 trillion (10¹²) | A single machine's spec sheet |
| PH/s | 1 quadrillion (10¹⁵) | Hashprice, quoted per petahash a day |
| EH/s | 1 quintillion (10¹⁸) | Mining pools |
| ZH/s | 1 sextillion (10²¹) | The whole network, about 1.0 today |
A 600 TH/s machine makes 600 trillion guesses a second and still needs decades alone
Take the Antminer S23 XP Hyd, which our store lists at 600 TH/s drawing 5,340 W. It makes 600 trillion guesses every second, which is 5.2 × 10¹⁹ in a day. Against 6.04 × 10²³ guesses for a block, that is an average of 31.9 years to win one block on its own, at today's difficulty.
That is why machines work in a pool. The pool adds up everyone's guesses, wins blocks often and pays each machine for the share of the guesses it contributed. The machine's share of the network is 600 trillion out of about 10²¹, roughly one in 1.7 million. A share that size of the 450 new bitcoin paid out each day is about 0.00027 bitcoin, which is about $22 at $82,800, before transaction fees and the pool's cut, and at today's difficulty.
The share is the thing being paid, and nothing is lost by the machine never winning a block itself.
Six hundred trillion guesses a second is about one 1.7-millionth of the network.
TH/s counts guesses, not value, so read it with J/TH
Two machines with the same TH/s make the same guesses and earn the same coins at the same difficulty. What separates them is what each guess costs in electricity. The S23 XP Hyd draws 5,340 W for 600 TH/s, which is 8.9 joules for every terahash, written J/TH. A machine that needs 17 J/TH to make the same 600 TH/s draws nearly twice the power for the same coins. The spec sheet guide puts both numbers side by side, and efficiency and halvings shows why the second one decides how long a machine stays worth switching on.
It also explains a number that confuses new owners. The hashrate a pool shows for your machine is counted from the guesses it receives over a window, so it wanders around the spec sheet figure, as why your miner's hashrate reads lower than its spec sheet explains.
Finally, a bigger network does not mean bigger rewards. When more machines join, the network makes more guesses, each block still pays 3.125 new bitcoin, and every machine's share shrinks until difficulty rises to match.
Three questions to ask when you see a hashrate
On a spec sheet, a pool page or a hosting quote, a hashrate figure is always answering the same three questions. Is it TH/s, PH/s or EH/s? Without the unit the number means nothing, and a thousand-fold slip is easy to make when the figures run into the hundreds.
Is it the machine's rating or what a pool has counted? The first is a promise from the maker and the second is a measurement over a window, and they rarely match to the digit. And what does the machine draw to make it? The J/TH figure answers that, and it is the one that turns guesses into a cost.
What it means for a miner
Your machine's TH/s is its slice of a very large number, and the slice is what you are paid on. The spec sheet fixes how big the slice is. What moves is the number under it: the network's guesses, which is difficulty.
That is why the figures to follow are the machine's J/TH, what it costs to run at your power rate, and the network's difficulty. Hash count on its own says how many guesses, and never how much a coin costs to make. A machine that makes its guesses for fewer joules makes more coins per unit of electricity, and keeps making them for longer.
Sources and further reading
- Block 971712 — mempool.space, Accessed 19 Oct 2026
Disclosure
Firsthand Bitcoin sells and hosts mining hardware, including this machine. No manufacturer, distributor or affiliate programme paid for or reviewed this page and we take no commission on the links above. Historical figures are computed from daily bitcoin price and network hashprice, each day valued at its own prices. Nothing here is investment advice.