user4546: In the following list I always see difficulty values like 2^-12
How to calculate the actual difficulty from it?
Comparison of mining pools

user13700: First of all, actual difficulty is defined as the number d such that the probability of a random hash being valid is 1/(d*2^32). In other words, the hash needs to have at least 32 + log_2(d) zeros in front of it to be valid. (This is not exactly the case if d is not a power of 2, but you get the general idea.)
In that article, a difficulty of 2^-12 means that the probability of a random share being valid is 1/(2^-12 * 2^32) = 2^-20. Note that typically, pool difficulty, is measured in multiples of 2^-16 for reasons discussed in the article, so a difficulty of 2^-12 would be a pool difficulty of 2^4 = 16.

4546: <p>In the following list I always see difficulty values like 2^-12
How to calculate the actual difficulty from it?</p>

<p><a href="https://github.com/litecoin-project/litecoin/wiki/Comparison-of-mining-pools" rel="nofollow">Comparison of mining pools</a></p>
 13700: <p>First of all, actual difficulty is defined as the number <code>d</code> such that the probability of a random hash being valid is <code>1/(d*2^32)</code>. In other words, the hash needs to have at least <code>32 + log_2(d)</code> zeros in front of it to be valid. (This is not exactly the case if <code>d</code> is not a power of 2, but you get the general idea.)</p>

<p>In that article, a difficulty of <code>2^-12</code> means that the probability of a random share being valid is <code>1/(2^-12 * 2^32) = 2^-20</code>. Note that typically, pool difficulty, is measured in multiples of <code>2^-16</code> for reasons discussed in the article, so a difficulty of <code>2^-12</code> would be a pool difficulty of <code>2^4 = 16</code>.</p>
