How to know "Current Total Coins"

[Skully]

How do you determine the current total coins ( for btc or another alt coin )?

I'm trying to do a calculation to understand the current market cap for new coins that come out onto the market.

[DeathAndTaxes]

Each coin will have a new coin subsidy schedule.

For Bitcoin it began at 50 BTC for the first 210,000 blocks and then it halves (technically a binary right shift) every 210,000 blocks.  With the blockcount and a a little math you can compute the total # of coins in circulation *.  Keep in mind the block count begins at #0 (genesis block) so when looking at sites which report the block height or block # adjusted by one.

At block #209,999 it would be 210,000 * 50 = 10,500,000 BTC.
At block #210,000 it would be 210,000 * 50 + 1 * 25 = 10,500,025 BTC.
At block #284,681 it would be 210,000 * 50 + 64,682 * 25 = 12,117,050 BTC.


* For Bitcoin (and I assume all copycat clones) this only provides you an estimate because technically a miner can choose to receive a smaller subsidy (but not larger).  So right now your mining pool "could" decide to put a subsidy of zero in instead of 25 BTC.  Of course there is no reason to do so but due to bugs in mining code there are a dozen or so blocks where the subsidy is less than the max allowed.  A pool generating a block with 24.9 (or zero) new coins would be valid, as would 25.0 new coins but 25.1 would not. Also due to a bug in early client version the 50 BTC in the genesis block (#0) is unspendable although it is generally included in the total coin count.