so i would say if you calculated how many coins were mined up until April 2011 (i am sure someone here will know this)

This is a pretty easy calculation (Since you only specified a month, I'll use the middle of the month, April 15):

- There are 60 minutes in an hour, 24 hours in a day, and 365.25 days in a year
- Multiply those together and you find there are about 525960 minutes in a year, and 1440 minutes in a day
- A new block is generated on average every 10 minutes.
- Divide the minutes per year (and per day) by 10 minutes per block to find out on average how many blocks are generated in that time
- So, we get about 52596 blocks per year and 144 blocks per day
- Satoshi started bitcoin on 2009 January 3
- There are 2 years between 2009 January 3 and 2011 January 3
- There are 28+28+31+15= 102 days between 2011 January 3 and 2011 April 15
- 2 years * 52596 blocks per year = 105192 blocks
- 102 days * 144 blocks per day = 14688 blocks
- So, by mid-April 2011 there were approximately 105192 + 14688 = 119880 blocks
- The block subsidy back then was 50 BTC per block.
- 50 BTC per block * 119880 blocks = approximately 5994000 bitcoins mined

If you look at

blockchain.info you'll see that my calculated "estimate" of 119880 blocks on April 15 is close, but not exact:

https://blockchain.info/block-height/119880The 119880'th block was actually generated on April 24. If we click on the "Previous Block" hash over and over, eventually we get back to the 118412'th block which was the first block generated on April 15.

So if you multiply 118412 blocks * 50 BTC per block, you find that by exactly mid April there should have been

**exactly 5920600 bitcoins mined**.

Looks like my "estimate" was pretty close. It's the difference between saying "5.99 million BTC" and "5.92 million BTC".

Then it would be a safe bet i think to say that the amount up until then would be like a maximum that could be missing, but more likely about 20-50% of those early mined coins mined prior to Arpil 2011

20% * 5920600 BTC = 1184120 BTC

50% * 5920600 BTC = 2960300 BTC