why bitcoin has 21million supply

[cafter]

Why was the decision made to cap the total supply of Bitcoin at 21 million BTC specifically? it could be 10million, 100million, why the specific number "21"
was it a deliberate and well thought out decision, or was it a bit arbitrary? 
i wanted to understand the reasoning behind this particular number "21" and whether any historical or technical factors played a role in determining it.

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[Upgrade00]

Firstly the Bitcoin total supply is not 21 million but is actually 20999999.9769BTC which is then rounded up to the closest whole figure which is 21 million.

Then to the reason for why ~21 million was chosen it was most likely just a random number which was the result of the aggregation of the coinbase rewards starting from 50BTC and then gradually getting halved every 210,000 blocks until we get to zero.

Check out this thread for more information - https://bitcointalk.org/index.php?topic=1090560.0

[satscraper]

Why was the decision made to cap the total supply of Bitcoin at 21 million BTC specifically? it could be 10million, 100million, why the specific number "21"
was it a deliberate and well thought out decision, or was it a bit arbitrary?  
i wanted to understand the reasoning behind this particular number "21" and whether any historical or technical factors played a role in determining it.

There are plenty of speculations on this matter which pound a square peg into a round hole. My personal explanation is as simple as following. Bitcoin was invented at the dawn of the twenty-first century. Consequently, 21 was chosen by Satoshi just as symbolic number to emphasize that BTC is the money for the 21^st century.

[_act_]

Why was the decision made to cap the total supply of Bitcoin at 21 million BTC specifically? it could be 10million, 100million, why the specific number "21"
was it a deliberate and well thought out decision, or was it a bit arbitrary? 
i wanted to understand the reasoning behind this particular number "21" and whether any historical or technical factors played a role in determining it.

Everything about bitcoin was deliberately done in a way that people are going to be encouraged to buy it. The reason Satoshi Nakamoto chose 21 million coins to be the total supply can not be known, only him can answer that. But the best answer people can have about it is because he wants bitcoin to have limited supply so that the coin can have value.

[EL MOHA]

I also was a bit curious why he actually choose that exact number and I did some little findings and some articles reported that satoshi’s choice was just a guess but an educated one
Here is a quote of his I saw

https://nakamotostudies.org/emails/satoshi-reply-to-mike-hearn/[/url]]
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.

And some on https://bitcoin.stackexchange.com/questions/8439/why-was-21-million-picked-as-the-number-of-bitcoins-to-be-created
did the mathematical calculations as

Calculate the number of blocks per four 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.

Should note that the 6 blocks per hour was as a result of 10 minutes set as time for mining of each block

[Faisal2202]

Well, the question is quite interesting and i never came to think about it because i thought its just a random number. Because, there are more than 20 thousands tokens available in the market and all of them have different numbers of supply. Which to some projects have some meaning and to some projects they are just random. Well, after reading the mentioned topic by Upgrade00, i found some answers which are mostly the same. So here is what most of the people think about why the supply is set to 21 million.

Satoshi Nakamoto settled on a target time of 10 minutes per block with an initial subsidy of 50 BTC set to halve once every 4 years.

4 years / 10 minutes ≈ 210 000
50 + 25 + 12.5 + 6.25 + ... = 100
210 000 * 100 = 21 million

Now, if we look at the calculations, why the number of 4 years is kept 4. as why halving is always after 4 years, well, i assume if we would change the halving years then the block numbers of 210 000 will also be different. So, overall, one thing i am seeing here is, Satoshi kept the supply according to halving periods not according to some random shit.

Means, he must have some plans for future too, maybe he could be online again.

[sheenshane]

Why was the decision made to cap the total supply of Bitcoin at 21 million BTC specifically? it could be 10million, 100million, why the specific number "21"
was it a deliberate and well thought out decision, or was it a bit arbitrary?  
i wanted to understand the reasoning behind this particular number "21" and whether any historical or technical factors played a role in determining it.

Only Satoshi will answer your question about why there's only 21 million total Bitcoin supply.
As the supply is fixed and not subject to inflation, some proponents argue that it could encourage saving and long-term investment in Bitcoin. However, it also has its criticisms, as deflationary assets might lead to hoarding behavior, hindering the currency's use in daily transactions.

The true reason behind the selection of 21 million Bitcoins may never be known, as Satoshi Nakamoto's identity and intentions remain a mystery to this day.  The decision has undoubtedly contributed to Bitcoin's unique properties and its status as the first and most valuable cryptocurrency in the world.

[SamReomo]

Why was the decision made to cap the total supply of Bitcoin at 21 million BTC specifically? it could be 10million, 100million, why the specific number "21"
was it a deliberate and well thought out decision, or was it a bit arbitrary? 
i wanted to understand the reasoning behind this particular number "21" and whether any historical or technical factors played a role in determining it.

You know that some people consider odd numbers like 7, 11, 21, 27, ... and others as the lucky numbers, and that's why making the total number of Bitcoin at 21 million would be a lucky thing for its users. I believe that the people who have faith in numerology knows better that some numbers can make projects far more luckier than the other numbers, and that can also be a reason to set the limit of Bitcoin to 21 million only.

Another important factor that might have been considered while limiting the total supply of Bitcoin to 21 million would be that the amount is quite a reliable amount to make a currency worth grow over time when it receives more purchases. The value of Bitcoin should be far lower if Satoshi has set its supply to something 100 million, and it would also require a lot more time to mine those 100 million Bitcoin.

While setting the value to 10 million would be a good thing to some extent but the total Bitcoin's should have already be mined till this date and the miners won't be getting incentivize for their effort of mining. I think Satoshi set that number according to a strategy that only he knew, and because of that Bitcoin is still working in its best way, and it's growing in value after each halving event.

[Flexystar]

Firstly the Bitcoin total supply us not 21 million but is actually 20999999.9769BTC which is then rounded up to the closest whole figure ehiu us 21 million.

Then to the reason for why ~21 million was chosen it was most likely just a random number which was the result of the aggregation of the coinbase rewards starting from 50BTC and then gradually getting halved every 210,000 blocks until we get to zero.

Check out this thread for more information - https://bitcointalk.org/index.php?topic=1090560.0

Thanks for the share mate. I just went through the thread to which you referred us. It seems there are number of justification for the 21 million number and thus lot of theories behind it.

However, I see that every one is trying to add up and substract the numbers, years, time in minutes, and much more! I think math's is funny language for this very reason. There is one problem and you can have N-number of solutions for the same. It's but obvious that we will never be able to look at the correct answer.

The closest one seems that it's just random number with block reward process as described by @Upgrade00

Some of the quotes from earlier discussion: It gets as interesting as you keep on digging more.

Start with a block reward of a nice simple number of 50 BTC per block.
Then every 210000 block (approximately every 4 years if blocks are generated on average every 10 minutes), cut the block reward in half and throw away any decimals after the 8th decimal place.
So after 210000 blocks you will have generated 50 * 210000 = 10500000 BTC
Then after another 210000 blocks you will have generated another 25 * 210000 = 5250000 BTC for a total of 10500000 + 5250000 = 15750000 BTC
Then after another 210000 blocks you will have generated another 12.5 * 210000 = 2625000 BTC for a total of 10500000 + 5250000 + 2625000 = 18375000 BTC

4 years / 10 minutes ≈ 210 000
50 + 25 + 12.5 + 6.25 + ... = 100
210 000 * 100 = 21 million

A double precision floating point has 52 significant bits so is capable of describing every number between 0 - 4503599627370496 exactly.
Or converting that number of satoshi's in Bitcoins this gives
45,035,996. 27370496
So whilst he could have use 45 million my guess is that the maths of starting with 50BTC and halving came to ~21 million which is high enough to use the full range while giving some room for error such as someone doing
( coins in circulation + satoshi's stash ) / 2  and not worrying about overflow errors.

[Lucius]

Why was the decision made to cap the total supply of Bitcoin at 21 million BTC specifically? it could be 10million, 100million, why the specific number "21"
~snip~

Maybe he just liked playing Blackjack, and maybe he was 21 at the time he started Bitcoin

~snip~
Means, he must have some plans for future too, maybe he could be online again.

Of course, he will certainly appear after 10+ years to clear up the mystery behind the number 21

[Aanuoluwatofunmi]

After considering every reasons why bitcoin has that particular figure rounded up to 21 million dollars, let's also compare and contrast the fiat currency with bitcoin, you keep minting new currency in the fiat economy and there's no limit to how these money comes in because they are centralized, bitcoin has a finite supply, there's no way to make any form of manipulations with it's supply as we have in fiat, money should be circulating and not centralized, this is one of the things bitcoin has come to serve humanity.

[Upgrade00]

Satoshi Nakamoto, the creator of Bitcoin, defined 21 million wahoos for this wish, but if it becomes more prominent, each unit will be crushed more,

This will only be done if there is a consensus agreement which will only happen when such a need for it becomes absolutely evident, which I don't see coming anytime soon.

currently each unit is 1000 satoshis.

Wrong.
Currently, 1BTC is 100,000,000 satoshis

[Crypto Library]

Actually the question created a curious one in my mind. Maybe the same curiosity was in your mind that's why you created this topic.
However, after seeing your topic, I explored a bit, but still the subject is very confusing to me.  But initially, the answer to this question in my head is that the reason for the supply of 21 million bitcoins is to create a limitation.
Since Satoshi created the revolution Bitcoin , his purpose was to create a new economic system to protect privacy and avoid the ongoing fiat currency inflation etc. Satoshi is a very intelligent man, there must be a reason behind it, maybe it is a secret just like he is hidden from us.

[Stepstowealth]

i wanted to understand the reasoning behind this particular number "21" and whether any historical or technical factors played a role in determining it.

There may not be any big deal to it, it could have been any number and we will still be wondering why that number was chosen. Satoshi had to make a choice concerning the limit in supply of bitcoins, and they chose the number that they were okay with. Many of the answers will be guesses, only Satoshi can really know, and we may be surprised the reason behind it, maybe it was his lucky number or some other thing because one thing with nerds is that they can give serious projects names from other things that they personally like.

[Mpamaegbu]

OP, you may want to see (read in this case) Why 21 million bitcoins? Why was ~that~ number chosen? It's a thread made on June 15, 2015 on this same issue you seek. The question was answered there in less than 20 posts.

[Rikafip]

Firstly the Bitcoin total supply is not 21 million but is actually 20999999.9769BTC which is then rounded up to the closest whole figure which is 21 million.

Lol @ the nitpicking. When/if someone asks you what's bitcoin total supply, do you say 20999999.9769 or 21 million?  

OP, you may want to see (read in this case) Why 21 million bitcoins? Why was ~that~ number chosen? It's a thread made on June 15, 2015 on this same issue you seek. The question was answered there in less than 20 posts.

The very same link was shared in the first reply of this thread by Upgrade00.  

[Hamza2424]

Casually answer why Bitcoin has a 21M supply because Satoshi wanted 21M. I think there can be no further need for explanation, also what a weird question haha I had never thought about it, like it sounds similar to why the universe is called Universe haha, first of all try to focus on having 1 from the 21M, if you already have congratulations now focus on having 10 and so on.

  I will definitely ask Satoshi if he can meet me somewhere, Until that time follow my above instructions.

Now, if we look at the calculations, why the number of 4 years is kept 4. as why halving is always after 4 years, well, i assume if we would change the halving years then the block numbers of 210 000 will also be different. So, overall, one thing i am seeing here is, Satoshi kept the supply according to halving periods not according to some random shit.

Means, he must have some plans for future too, maybe he could be online again.

Haha. He's reading your post and he might be thinking why I hand over this to these idiots (Including me) who are discussing shit for nothing, rather than accumulating or finding a good strategy to accumulate and bring my mission to its glory. my innocent question is, let's consider it a random shit so what, or on the same let's consider it a preplanned so what? Is it helping you out to grab an amount of it? No So why...