By what mechanism the total quantity of bitcoin is limited to 21 millions?

[steve2035]

Could someone explain me how the total quantity of bitcoin is limited to 21 millions?

How this limit has been defined?

Please, don't tell me it is written in the program 

[1713953682]

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[1713953682]

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[OmegaStarScream]

This question[1][2][3] has been asked before by multiple people (I believe Satoshi never said why though):

[1] https://bitcoin.stackexchange.com/questions/8439/why-was-21-million-picked-as-the-number-of-bitcoins-to-be-created
[2] https://www.quora.com/Why-is-Bitcoins-cap-set-at-circa-21-million-coins-and-not-more-or-less-Is-this-amount-chosen-in-an-arbitrary-way-or-is-there-an-argument-behind-it
[3] https://bitcointalk.org/index.php?topic=3366.20

The mathematical answers regarding the block reward and the number of blocks are the ones that make more sense.

[ranochigo]

Could someone explain me how the total quantity of bitcoin is limited to 21 millions?
Please, don't tell me it is written in the program 

It is. The way mining works is that the miners will mine blocks with the correct block reward and that is the way that Bitcoins are distributed. The block reward is coded into the clients and they will only accept blocks with the correct block reward and that is how they have a limited supply.

However, its not perfect and it is impossible for it to be exactly 21 million Bitcoins. Even if it can be, the earlier miners had poorly written client that resulted in incorrect block rewards being claimed and thus the exact value is far from 21million Bitcoins.

[lukaexpl]

Could someone explain me how the total quantity of bitcoin is limited to 21 millions?
Please, don't tell me it is written in the program 

It is. The way mining works is that the miners will mine blocks with the correct block reward and that is the way that Bitcoins are distributed. The block reward is coded into the clients and they will only accept blocks with the correct block reward and that is how they have a limited supply.

However, its not perfect and it is impossible for it to be exactly 21 million Bitcoins. Even if it can be, the earlier miners had poorly written client that resulted in incorrect block rewards being claimed and thus the exact value is far from 21million Bitcoins.

So is it more then 21 million or less?

Am I correct in thinking that one could hard fork and make total supply any arbitrary number?

[ranochigo]

Could someone explain me how the total quantity of bitcoin is limited to 21 millions?
Please, don't tell me it is written in the program 

It is. The way mining works is that the miners will mine blocks with the correct block reward and that is the way that Bitcoins are distributed. The block reward is coded into the clients and they will only accept blocks with the correct block reward and that is how they have a limited supply.

However, its not perfect and it is impossible for it to be exactly 21 million Bitcoins. Even if it can be, the earlier miners had poorly written client that resulted in incorrect block rewards being claimed and thus the exact value is far from 21million Bitcoins.

So is it more then 21 million or less?

Less.

Am I correct in thinking that one could hard fork and make total supply any arbitrary number?

Yes. If you modify your client to have 50 million BTC as the total supply, you will have created a fork. Only those who have modified their rules to yours will follow your chain. The other clients who do not support you will still be following the 21 Mil Bitcoin total supply rule. You will essentially have created an altcoin.

[DooMAD]

To see the numbers involved in terms of block reward over time, check out Projected Bitcoins Long Term on the Bitcoin Wiki.  We're currently still in "reward era 3", or 12.5 newly created BTC per block.  As for "why", it's claimed that Mike Hearn was given the following reply by Satoshi via email on the subject of how 21 million was chosen (source):

My choice for the number of coins and distribution schedule was an educated guess. It was a difficult choice, because once the network is going it's locked in and we're stuck with it. I wanted to pick something that would make prices similar to existing currencies, but without knowing the future, that's very hard. I ended up picking something in the middle. If Bitcoin remains a small niche, it'll be worth less per unit than existing currencies. If you imagine it being used for some fraction of world commerce, then there's only going to be 21 million coins for the whole world, so it would be worth much more per unit. Values are 64-bit integers with 8 decimal places, so 1 coin is represented internally as 100000000. There's plenty of granularity if typical prices become small. For example, if 0.001 is worth 1 Euro, then it might be easier to change where the decimal point is displayed, so if you had 1 Bitcoin it's now displayed as 1000, and 0.001 is displayed as 1.

[aleksej996]

Could someone explain me how the total quantity of bitcoin is limited to 21 millions?
Please, don't tell me it is written in the program 

It is. The way mining works is that the miners will mine blocks with the correct block reward and that is the way that Bitcoins are distributed. The block reward is coded into the clients and they will only accept blocks with the correct block reward and that is how they have a limited supply.

However, its not perfect and it is impossible for it to be exactly 21 million Bitcoins. Even if it can be, the earlier miners had poorly written client that resulted in incorrect block rewards being claimed and thus the exact value is far from 21million Bitcoins.

So is it more then 21 million or less?

Am I correct in thinking that one could hard fork and make total supply any arbitrary number?

You could also hard fork and have all the 21 million for yourself and nobody else, but it is not really Bitcoin then, is it?
Bitcoin is the largest (based on the difficulty of computation) blockchain with certain rules, that define blockchain itself. One of these rules as a consequence have that there will only be 21 million BTC. A hard fork can be anything, you can make as a rule that every block needs to contain a picture of a cat, but that is a whole different program. There are only limitations on a soft fork (old clients need to accept the fork), not a hard fork.

[AGD]

Could someone explain me how the total quantity of bitcoin is limited to 21 millions?
Please, don't tell me it is written in the program 

It is. The way mining works is that the miners will mine blocks with the correct block reward and that is the way that Bitcoins are distributed. The block reward is coded into the clients and they will only accept blocks with the correct block reward and that is how they have a limited supply.

However, its not perfect and it is impossible for it to be exactly 21 million Bitcoins. Even if it can be, the earlier miners had poorly written client that resulted in incorrect block rewards being claimed and thus the exact value is far from 21million Bitcoins.

So is it more then 21 million or less?

Am I correct in thinking that one could hard fork and make total supply any arbitrary number?

You can create a hard fork in a few minutes with any amount of total supply.

[bountyhunter1313]

This question[1][2][3] has been asked before by multiple people (I believe Satoshi never said why though):

[1] https://bitcoin.stackexchange.com/questions/8439/why-was-21-million-picked-as-the-number-of-bitcoins-to-be-created
[2] https://www.quora.com/Why-is-Bitcoins-cap-set-at-circa-21-million-coins-and-not-more-or-less-Is-this-amount-chosen-in-an-arbitrary-way-or-is-there-an-argument-behind-it
[3] https://bitcointalk.org/index.php?topic=3366.20

The mathematical answers regarding the block reward and the number of blocks are the ones that make more sense.

GREAT! THANKS.

[miguelmorales85]

21 MILLIONS, still I think he did not take into account the amount lost or burned. I think its not enough but can someone explain to me if this is possible, or its just better to add more zeroes after the point to make it more divisible.

[ranochigo]

21 MILLIONS, still I think he did not take into account the amount lost or burned. I think its not enough but can someone explain to me if this is possible, or its just better to add more zeroes after the point to make it more divisible.

It is possible to add more Bitcoins to the total supply but it will require a hard fork and it does not make sense economically. If you add more coins to BTC, there will be a higher supply of BTC and each of the BTC will drop in value. That is obviously not what anyone wants and everyone is likely going to oppose it. If you are going to add the number of decimals, that would make a far lot more sense with no one losing out.

Honestly, I don't see a need for that either. Unless each satoshi is worth $1, there is honestly no need for more decimals. Think about how much a Bitcoin would cost and the probability of it happening is very low.

[TwoSides]

I was thinking why is it only 21 millions and there are more or less 16 millions left to be mined? Why don't we have an unlimited supply so everyone including myself can mine atleast 1BTC in the future? Reading your comment made me realize that this is a market, the law of supply and demand still applies. There should always be a limit and difficulty in having one btc so that its value goes up.

If you add more coins to BTC, there will be a higher supply of BTC and each of the BTC will drop in value. That is obviously not what anyone wants and everyone is likely going to oppose it.

[aleksej996]

I was thinking why is it only 21 millions and there are more or less 16 millions left to be mined? Why don't we have an unlimited supply so everyone including myself can mine atleast 1BTC in the future? Reading your comment made me realize that this is a market, the law of supply and demand still applies. There should always be a limit and difficulty in having one btc so that its value goes up.

It isn't necessary. In future you should be able to cover the mining costs with the mining fees. You can still get bitcoins without increasing the supply.

[Forbiddenone]

the code was made like that,why dont it increased because there should be a limit to a supply whether it is 21 or more,there should be limit so price per coin can be decided.you can compare it with stock market. where there is fixed share so price can be decided for the market.

[bitpeepcom]

I was thinking why is it only 21 millions and there are more or less 16 millions left to be mined? Why don't we have an unlimited supply so everyone including myself can mine atleast 1BTC in the future? Reading your comment made me realize that this is a market, the law of supply and demand still applies. There should always be a limit and difficulty in having one btc so that its value goes up.

Roughly 16 Million coins are already mined..