The difficulty adjustment formula

explained by Satoshi Nakamoto

February 25, 2010

bitcointalk.org

the formula is based on the time it takes to generate 2016 blocks. The difficulty is multiply by 14/(actual days taken). For instance, this time it took 9.4 days, so the calculation was 14/9.4 = 1.49. Previous difficulty 2.53 * 1.49 = 3.78, a 49% increase