I read this article:

We have paid 0.034 BTC for the 10 GH/s ... Yesterday we have received our first daily payout and it was exactly 0.00041279 BTC ... Doing a quick calculation has shown that if the Bitcoin network difficulty remains the same and the daily payout is also the same as the one we got the first day we are going to need a little over 82 days to get back what we have spent for the mining contract.

In this case BTC per GH/s is 0.00041279/10 BTC/(GH/s). All of this is in one day, but for simplicity I removed day from the units.

Will buying more GH/s increase BTC per GH/s (in one day)? Since there is more power solving the problem, and there would be more probability to solve the problems?

How could I calculate decrease of BTC/day vs time with a fixed hashing speed?

  • You probably didn't pay for 10GH/s but more like 10GH/s for one month or one year? Important distinction.
    – Jannes
    Oct 8 '14 at 10:11
  • yes, a contract is hashings/seconds during some time. But you can remove the duration of the contract from the units.
    – sites
    Oct 8 '14 at 16:18
  • Not if you want to know if you're ever going to break even. (Supposing you can correctly estimate the difficulty growth.) You yourself mention 82 days, but not the contract duration. I now saw the linked article (hadn't before) : 5 years. Anyway. looks even more like a scam than it did before. Also the article is clueless on proper use of units... GHS? You seem to be using units properly. Anyway, you have your answer(s) below.
    – Jannes
    Oct 8 '14 at 17:58

The short answer is: No. The average number of bitcoins per hash is fixed, and is roughly equal to B / (2^32 * D), where B is the bitcoins per block and D is the difficulty. Every calculated hash is either a block or not; if it's not, it doesn't bring you any closer to finding a block.

However, for completeness it should be noted that there are several sophisticated attacks that allow superlinear gains on hashrate, such as lie-in-wait and hashrate amplification (also known as selfish mining). Superlinearity can also be a side effect of a short block interval. All of these require huge hashrate to be effective, on the order of a quarter of the network hashrate - not something which should be of concern to the average miner.

  • I was asking bitcoin per (hash per second), i.e. BTC/(h/s),I know BTC per hash is subject to probability, but if I buy more hashes per second probability increases?
    – sites
    Oct 8 '14 at 16:20
  • @juanpastas: No. If you have twice the hashes/second, then every second you have twice the hashes and get twice the bitcoins. Oct 13 '14 at 15:22

The expected number of bitcoins per hash depends only on the network difficulty and block reward, not the speed at which you execute the hashes. Every hash computed has exactly the same probability of successfully mining a block (or share, in the case of pool mining), and this probability is a function of the difficulty only. More powerful hardware does more hashes per second, so the expected bitcoins earned per second increases, but bitcoins per hash does not change.

  • I was asking bitcoin per (hash per second), i.e. BTC/(h/s),I know BTC per hash is subject to probability, but if I buy more hashes per second my probability increases?
    – sites
    Oct 8 '14 at 16:11
  • @juanpastas: If you buy more hashes per second, then on average you earn more bitcoins per second. Each hash still earns you the same average number of bitcoins as before, but since you have more hashes in each second, you earn more coins per second. It's linear: buying twice as many GH/s earns you twice as many bitcoins per day (no more and no less), all other things being equal. Oct 8 '14 at 17:12
  • I see this as: a lot of computers are trying to solve the problem, if I have more computers(guesses), I will guess more times than others computers ( or group of computers), thus incrementing BTC per day. what am I missing?
    – sites
    Oct 8 '14 at 18:15
  • is having more hash speed like playing a raffle with more tickets?
    – sites
    Oct 8 '14 at 18:17
  • 1
    When you're part of a pool, you get paid for the work you do whether you find the block or someone else finds the block, so it's more like there is no raffle and you paid for the tickets you buy.
    – Tyler
    Oct 8 '14 at 21:56

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