# What are the odds of discovering a block as a solo miner?

I understand that during mining, one does not discover individual coins, but rather blocks of coins, and I heard that one block equals many coins (but how many?). I am wondering though, as a solo miner, what are the odds of discovering a new block? I guess this depends on my hardware but if we say that a GPU is 10 times faster than a CPU, and a \$10 USB ASIC device is 1000 times faster than a CPU, and a \$300 mining box is 5000 times faster than a CPU, perhaps one can adjust the odds estimations to reflect that.

Also, how many BTC would I obtain if I discovered a block? This website http://blockexplorer.com/ seems to how a variable number. But it seems a bit like winning a lottery.

• It is hard to calculate that, as bitcoins are less and less discovered over time. Answer depends on time period of mining. – blogger Nov 5 '13 at 2:09
• When I signed up for btcguild today, I found that blocks were frequently being discovered. One every few minutes. But they have zillions of hashes per second going on. – Friendly Nov 5 '13 at 2:16
• Related question: bitcoin.stackexchange.com/questions/16687/… – Isac Sep 10 '15 at 8:47

Take the total network Th/s and divide by your total Th/s. That number gives you you a number that tells you how many blocks will occur before you get one (on average).

So if there is currently 3,666 Th/s on the network, and you have a 0.55 Th/s (like you would if you have a \$5,000 KNCMiner Jupiter ASIC), then 3,666/0.55 = 6,665.

That means you have 1/6,665ths of total hashing capacity. There will be 6,665 blocks before you get one.

So if there are 144 blocks in a day, then you need to wait 46.28 days to get a block when mining solowith that hardware. But that is assuming difficulty doesn't rise. So what will happen with a rising difficulty is you end up waiting much longer even, and possibly never end up getting a block when solo mining.

That's why solo mining is not as profitable as using a pool for anyone without tens of Th/s nowadays.

• Or in the case of a USB miner, which mines maybe 5 GH/s, it would be 4600 days or 12.5 years. And with a CPU miner the chances are 1000 times worse, i.e. infitesimal. So really without good hardware this is like playing the lottery. – Friendly Nov 5 '13 at 4:22
• note that the p of {finding a block in X blocks when your chance of mining a block in one unit of time is 1/x} = (1-(6664/6665)^6665) is about .632, so you would actually only need to be mining for about 4605 blocks with .5 probability. Now that the difficulty is about 600 times harder, this is probably a moot point. – hedgedandlevered Aug 20 '14 at 1:27

how many BTC would I obtain if I discovered a block?

25 BTC in a single block currently. This will change over time as less and less BTC are available to mine

Here is an excerpt from bitcoin wiki:

How are new bitcoins created?

New bitcoins are generated by the network through the process of "mining". In a process that is similar to a continuous raffle draw, mining nodes on the network are awarded bitcoins each time they find the solution to a certain mathematical problem (and thereby create a new block). Creating a block is a proof of work with a difficulty that varies with the overall strength of the network. The reward for solving a block is automatically adjusted so that, ideally, every four years of operation of the Bitcoin network, half the amount of bitcoins created in the prior 4 years are created. A maximum of 10,499,889.80231183 bitcoins were created in the first 4 (approx.) years from January 2009 to November 2012. Every four years thereafter this amount halves, so it should be 5,250,000 over years 4-8, 2,625,000 over years 8-12, and so on. Thus, the total number of bitcoins in existence can never exceed 20,999,839.77085749 and counting. See Controlled Currency Supply.

Blocks are mined every 10 minutes, on average and for the first four years (210,000 blocks) each block included 50 new bitcoins. As the amount of processing power directed at mining changes, the difficulty of creating new bitcoins changes. This difficulty factor is calculated every 2016 blocks and is based upon the time taken to generate the previous 2016 blocks.

To answer you question about what is the reward for mining a valid block. Currently 25 BTC, previously it was 50 BTC until block number 210,000 was mined. The current amount will be divided by 2 when block number 420,000 is mined.

That said the fluctuation in amounts you see on mined blocks is the transaction fees. When people send bitcoin they have choice to include a mining fee (to get better chance of getting in next block faster than other transactions). Depending on the transactions your miner decide to include you will get more or less bitcoin plus the base reward of 25 BTC. So normally miners that wants to cut a profit will favorite transaction with bigger fee.

The difficulty changing won't preclude you from finding a block. However because it's essentially random, there's a chance you might never find a block, and also a chance you could find one on the first hash. There's even a chance you could find 10 in a row. It's random, like flipping a fair coin. Each try is also independent, also like flipping a coin. Just because you've flipped the coin 10/ times and it comes up tails, doesn't mean your "due" for it to come up heads. It's still 50/50.