Topic: Why was 21 million coins chose as the total number of bitcoins? (Read 3610 times)
I do not think Satoshi chose it intentionally, he chose it randomly.
In a slightly earlier version of Satoshi's code (pre-genesis) the limit was 20 million bitcoins. Blocks were set to arrive every 15 minutes with an initial subsidy of 100 BTC set to halve every 100`000 blocks (about 2 years and 10 months).
Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
Interesting - where is this code available to support your claim (not that I don't believe you, but I'd like to see it).Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
I'm surprised I didn't provide a link to begin with. I must have been in a hurry.
Cryddit posted the source of an alpha snapshot of the reference client here. Search the page for "GetNextWorkRequired". You should find all the information you're looking for within this function.
Please let me know if you end up with different numbers. I routinely screw up idle calculations.
Highly interesting! I always find it very interesting to see early versions or concepts of things and like to dig around to see what has changed and what remained until the final version. I think the most important factor is that every basic addition of an amount must be doable with a given integer representation using 64 bit, yeah!
In a slightly earlier version of Satoshi's code (pre-genesis) the limit was 20 million bitcoins. Blocks were set to arrive every 15 minutes with an initial subsidy of 100 BTC set to halve every 100`000 blocks (about 2 years and 10 months).
Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
Interesting - where is this code available to support your claim (not that I don't believe you, but I'd like to see it).Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
I'm surprised I didn't provide a link to begin with. I must have been in a hurry.
Cryddit posted the source of an alpha snapshot of the reference client here. Search the page for "GetNextWorkRequired". You should find all the information you're looking for within this function.
Please let me know if you end up with different numbers. I routinely screw up idle calculations.
Total number of bitcoins to ever exist is 20999999.97690000, a little less than 21 million. 
No, as discussed on this thread:https://bitcointalksearch.org/topic/what-would-you-pay-for-the-keys-to-the-genesis-blockaddress-1029082
at least "150 + a bit" of those coins never existed in the first place (3 unspendable coinbases + miners refusing the full reward + fees).
In a slightly earlier version of Satoshi's code (pre-genesis) the limit was 20 million bitcoins. Blocks were set to arrive every 15 minutes with an initial subsidy of 100 BTC set to halve every 100`000 blocks (about 2 years and 10 months).
Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
Interesting - where is this code available to support your claim (not that I don't believe you, but I'd like to see it). Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
The answer to the universe and everything is 42.
I love that book series. =)
Me
As a play on the ridiculousness of the legal age to drink alcohol being 21
Legal drinking age is 18 in many European countries.
16 in my country, but soon to be 18.
Total number of bitcoins to ever exist is 20999999.97690000, a little less than 21 million.
I think it is correlated with "gold" , but I'm not sure (surely I'm wrong).
21 million was not chosen, 21 million is the result of multiple other choices.
Initial block reward was 50BTC
1 block is made every 10 minutes
Block reward halves every 4 years
Those three choices lead to 21 million coins, after so many halvings the block reward eventually hits 0 and at that time the number of coins generated happens to be just under 21 million.
Initial block reward was 50BTC
1 block is made every 10 minutes
Block reward halves every 4 years
Those three choices lead to 21 million coins, after so many halvings the block reward eventually hits 0 and at that time the number of coins generated happens to be just under 21 million.
Nice answer, thanks for spelling it out like that.
As escrow.ms shared , the link provides a proper mathematical explanation on this
Calculate the number of blocks per 4 year cycle:
6 blocks per hour
* 24 hours per day
* 365 days per year
* 4 years per cycle
= 210,240
~= 210,000
Sum all the block reward sizes:
50 + 25 + 12.5 + 6.25 + 3.125 + ... = 100
Multiply the two:
210,000 * 100 = 21 million.
Economically, because the currency is effectively infinitely divisible, then the precise amount doesn't matter, as long as the limit remains fixed.
Calculate the number of blocks per 4 year cycle:
6 blocks per hour
* 24 hours per day
* 365 days per year
* 4 years per cycle
= 210,240
~= 210,000
Sum all the block reward sizes:
50 + 25 + 12.5 + 6.25 + 3.125 + ... = 100
Multiply the two:
210,000 * 100 = 21 million.
Economically, because the currency is effectively infinitely divisible, then the precise amount doesn't matter, as long as the limit remains fixed.
In a slightly earlier version of Satoshi's code (pre-genesis) the limit was 20 million bitcoins. Blocks were set to arrive every 15 minutes with an initial subsidy of 100 BTC set to halve every 100`000 blocks (about 2 years and 10 months).
Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
Sounds reasonable to me
In a slightly earlier version of Satoshi's code (pre-genesis) the limit was 20 million bitcoins. Blocks were set to arrive every 15 minutes with an initial subsidy of 100 BTC set to halve every 100`000 blocks (about 2 years and 10 months).
Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
Certainly there was some thought put into the magnitude of the limit. While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 datatype (potentially useful for JSON-RPC).
What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.
My understanding is that the initial 50 BTC block reward was an arbitrary number, as was the 210k number of blocks between the times that the block subsidy chances.
The 21 million number is simply the result of using the two above arbitrary numbers. (although the fact the initial block reward and the number of blocks between block subsidy changes being arbitrary is speculation, I do not see any other reasonable explanation)
The 21 million number is simply the result of using the two above arbitrary numbers. (although the fact the initial block reward and the number of blocks between block subsidy changes being arbitrary is speculation, I do not see any other reasonable explanation)
Pretty sure, it was not a random number picked up. It was derived from a lot of thing, and he also thought about the future of the coin while doing that
Oh, I thought it was obvious. 21 million. 21 is half of 42, the answer to Life, the Universe and Everything. But Bitcoin is only only half the answer, because money isn't everything. And 21 million instead of 21 because 21 would make it sound like a blackjack game. There, does that make sense? (OK, I'm in a weird mood right now... ;-)
The question is-why not?
legendary
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yeah basically derived as other have people have mentioned. 50x210,000 will give you half that, and then you double it for the infinite series. the 210,000 is just a round number representing 4 years of 10 minute blocks.
So that if all gold speculation goes to Bitcoin (at the prices of 2009) the price of bitcoin would be 1000000$ 
If bitcoin goes above all electronic payment methods it would be around 240.000 USD per coin.
So instead of 21 million, he ended up deciding to multiply that number of units by 100 million. That's kind of different.
And if you follow the links, there is even more commentary on the limit of 21 million bitcoins -
I'll try not to be such an asshole in the future, but for some reason my patience always seems to run out when I'm dealing with you.
Yeah it's just me, and also the entire ignore list you're sharing so that everyone else can also ignore the people you ignore.
And if you follow the links, there is even more commentary on the limit of 21 million bitcoins -
I'll try not to be such an asshole in the future, but for some reason my patience always seems to run out when I'm dealing with you.
Yeah it's just me, and also the entire ignore list you're sharing so that everyone else can also ignore the people you ignore.
21 million was the intended number, it isn't "derived" in the sense that it's an arbitrary number. It was coded intentionally to produce 21 million.
Really?
Did you have a conversation with Mr. Nakamoto whereby he explained this to you?
No, Hal Finney and Ray Dillenger did.
Quote
Ray Dillenger recalls:
I remember this discussion, actually.
Finney, Satoshi, and I discussed how divisible a Bitcoin ought to be. Satoshi had already more or less decided on a 50-coin per block payout with halving every so often to add up to a 21M coin supply. Finney made the point that people should never need any currency division smaller than a US penny, and then somebody (I forget who) consulted some oracle somewhere like maybe Wikipedia and figured out what the entire world’s M1 money supply at that time was.
We debated for a while about which measure of money Bitcoin most closely approximated; but M2, M3, and so on are all for debt-based currencies, so I agreed with Finney that M1 was probably the best measure.
21Million, times 10^8 subdivisions, meant that even if the whole word’s money supply were replaced by the 21 million bitcoins the smallest unit (we weren’t calling them Satoshis yet) would still be worth a bit less than a penny, so no matter what happened — even if the entire economy of planet earth were measured in Bitcoin — it would never inconvenience people by being too large a unit for convenience.
https://thewealthofchips.wordpress.com/2014/10/01/why-bitcoin-is-and-isnt-ideal-money/
I remember this discussion, actually.
Finney, Satoshi, and I discussed how divisible a Bitcoin ought to be. Satoshi had already more or less decided on a 50-coin per block payout with halving every so often to add up to a 21M coin supply. Finney made the point that people should never need any currency division smaller than a US penny, and then somebody (I forget who) consulted some oracle somewhere like maybe Wikipedia and figured out what the entire world’s M1 money supply at that time was.
We debated for a while about which measure of money Bitcoin most closely approximated; but M2, M3, and so on are all for debt-based currencies, so I agreed with Finney that M1 was probably the best measure.
21Million, times 10^8 subdivisions, meant that even if the whole word’s money supply were replaced by the 21 million bitcoins the smallest unit (we weren’t calling them Satoshis yet) would still be worth a bit less than a penny, so no matter what happened — even if the entire economy of planet earth were measured in Bitcoin — it would never inconvenience people by being too large a unit for convenience.
https://thewealthofchips.wordpress.com/2014/10/01/why-bitcoin-is-and-isnt-ideal-money/
Danny Hamilton, you're not smart enough or important enough to back up how much of an asshole you are. Maybe take it down a few notches, especially when you're wrong and making a fool of yourself.
And yet the quote that you've posted specifically states:
Quote
Satoshi had already more or less decided on a 50-coin per block payout with halving every so often
So it appears that the 21 million is the derived amount that "50-coin per block payout with halving every so often" would "add up to".
That post you quoted isn't about how the 21 million was "decided", it is about the divisibility. It starts by pointing out that the "50-coin per block payout with halving every so often", which results in 21 million, had already been decided (but says nothing about why it was chosen), and then goes on to explain why 108 subdivisions were chosen.
I'll try not to be such an asshole in the future, but for some reason my patience always seems to run out when I'm dealing with you.
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