What exactly happens when all the 21 million Bitcoins have been miined?

[sron]

What exactly happens when all the 21 million Bitcoins have been miined?

[panda1]

The short answer is miners make money from charging transaction fees...something like that

[IntrepidMiner]

Not much of anything really.

The block reward goes from being a tiny pittance to nothing, and by that time transaction fees will have overtaken block reward as the primary source of income for miners. At least this is how I understand it.

Here's a relevant post from roughly a month ago, if you look through it it might answer some more of your questions (might not):
https://bitcointalk.org/index.php?topic=103160.0

[luffy]

it could be extended as well. 

[IntrepidMiner]

it could be extended as well. 

Read this as "We can fork a blockchain separate from Bitcoin," which is a powerful tool, but it won't completely change the current bitcoin as we know it.

[memvola]

it could be extended as well. 

The reward is halved every four years and current transaction value precision is 8 decimals, so the reward will not be exactly zero for more than a hundred years, and 21 million bitcoins will never be mined completely.

If the precision is increased during that time, say the year 2112, then this period will be extended, but the total number will still be a bit lower than 21 million.

[Graet]

What exactly happens when all the 21 million Bitcoins have been miined?

our children or grandchildren have a huge party even bigger than the one we will have in November when block reward halves

I certainly wont be alive to worry about it

[Gabi]

it could be extended as well. 

You are free to make luffyCoin where you extend it.

But i'll keep using bitcoin, with only 21million coins and not even one more 

[Aahzman]

What exactly happens when all the 21 million Bitcoins have been miined?

you'll have been dead for at least 40 years. Does it matter?

[warbdan]

I wonder why only 21 million. There are over 6 billion people in the world. How can we encourage everyone to use something they can't possibly ever have 1 of? Sure, there's enough for everyone to have pieces of 1, but by this rationale, BTC is EXTREMELY undervalued right now. They should be worth $100's in USD. This is a good thing for miners, but not so good for the casual BTC user with ,0004 BTC in their wallet who can't use it, LOL.

[aznjack31]

it'll be a sight to see if anyone of us are alive hahaha

[paraipan]

I wonder why only 21 million. There are over 6 billion people in the world. How can we encourage everyone to use something they can't possibly ever have 1 of? Sure, there's enough for everyone to have pieces of 1, but by this rationale, BTC is EXTREMELY undervalued right now. They should be worth $100's in USD. This is a good thing for miners, but not so good for the casual BTC user with ,0004 BTC in their wallet who can't use it, LOL.

Do you have 1 troy ounce of Gold ingot?

According to this 50 million troy ounces of Gold are mined every year, so there should be plenty for every human being already.

[memvola]

I wonder why only 21 million. There are over 6 billion people in the world. How can we encourage everyone to use something they can't possibly ever have 1 of? Sure, there's enough for everyone to have pieces of 1, but by this rationale, BTC is EXTREMELY undervalued right now. They should be worth $100's in USD. This is a good thing for miners, but not so good for the casual BTC user with ,0004 BTC in their wallet who can't use it, LOL.

0.00000001 BTC is called a Satoshi, and there will be 350,000 units for everyone.

[puck2]

I wonder why only 21 million. There are over 6 billion people in the world. How can we encourage everyone to use something they can't possibly ever have 1 of? Sure, there's enough for everyone to have pieces of 1, but by this rationale, BTC is EXTREMELY undervalued right now. They should be worth $100's in USD. This is a good thing for miners, but not so good for the casual BTC user with ,0004 BTC in their wallet who can't use it, LOL.

Yes, BTC was designed to be subdivided. I believe the working unit is 1 Satoshi, which is 0.000000 01 BTC

More info here https://en.bitcoin.it/wiki/FAQ#What_do_I_call_the_various_denominations_of_Bitcoins.3F

[DannyHamilton]

I wonder why only 21 million. . .

A block reward of 50 BTC per was chosen for a starting amount.  Then a decision was made to cut the block reward in half after every 210,000 blocks.  If you do the math you'll see that the total mined amount happens to work out to a bit less than 21,000,000 by the time the block reward drops below 0.00000001.

I don't know for sure, but I doubt that there was any specific intention to choose the number 21 million as an upper limit.  More likely 50 seemed like a reasonable amount to get things started, and then about 4 years was chosen to allow people to adjust to the new block reward before cutting it in half again.

The number 5,000,000,000 could have been chosen as a block reward, and the end amount would have been a bit less than 2,100,000,000,000,000.  But 5 billion as a block reward would have been a large number to work with on a regular basis until the currency caught on.  Perhaps if we just move the decimal over 8 places to the left and give that amount a name (sort of like a $100 bill being called a Benjamin) we could work with that new amount until we need to split it up more.  Here's an idea.  We can move the decimal 8 places to the right and call it a bitcoin.  Then as we need to split it up more we can come up with new names for the smaller denominations.  (perhaps using SI? milli-bitcoin, micro-bitcoin)  When we get all the way down to the original unit as it is stored in the blockchain per the protocol, we can call it a Satoshi or something like that.

Note: the italicized is meant to be humorous.  Unless I mis-typed an extra zero somewhere, this is the way it actually works.