user1307: Which and how much mathematical operations are required for the blockheader-to-blockhash operation and how fast would a human be able to calculate a single hash?
EDIT: For simplicity, I think it's a good idea to use the world record for mathematical calculations to make it a little more fair.

user5406: The user C121 on r/bitcoin explored this topic in the thread Mining Bitcoin by hand.
He states that it takes 3385 integer operations to calculate one double SHA-256 hash.
His conclusion was that you would reach about 0.00003 H/s, or in other terms, it would take about 9.4 hours for one hash, assuming the human in question could do a 32-bit operation in 10 seconds.
He also estimates that you would fill about seventy pages of paper with the calculations per hash.
Update:
As Mathias711 pointed out in the comments, Ken Shirriff actually calculated some SHA-256 operations manually and wrote an article about mining bitcoin with pencil and paper. He arrives at an estimate of 0.67 hashes per day, at a vastly uncompetitive energy consumption. ;)

1307: <p>Which and how much mathematical operations are required for the blockheader-to-blockhash operation and how fast would a human be able to calculate a single hash?</p>

<p>EDIT: For simplicity, I think it's a good idea to use the world record for mathematical calculations to make it a little more fair.</p>
 5406: <p>The user C121 on r/bitcoin explored this topic in the thread <a href="http://www.reddit.com/r/Bitcoin/comments/1r3wau/mining_bitcoin_by_hand/">Mining Bitcoin by hand</a>.</p>

<p>He states that it takes 3385 integer operations to calculate one double SHA-256 hash.</p>

<p>His conclusion was that you would reach <strong>about 0.00003 H/s</strong>, or in other terms, <strong>it would take about 9.4 hours for one hash</strong>, assuming the human in question could do a 32-bit operation in 10 seconds.</p>

<p>He also estimates that you would fill about <strong>seventy pages of paper</strong> with the calculations per hash.</p>

<p>Update:<br>
As Mathias711 pointed out in the comments, Ken Shirriff actually calculated some SHA-256 operations manually and wrote an <a href="http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html">article about mining bitcoin with pencil and paper</a>. He arrives at an estimate of <strong>0.67 hashes per day</strong>, at a vastly uncompetitive energy consumption. ;)</p>
