It changes with monetary ups and downs. Right now $1.52 American equals 1 English Pound.
1 UK £ = 1.56 United States dollars
1 United States dollar = 0.64 UK £s
Assuming the question refers to USA Dollars, and UK pounds, about 1.6 at the moment (Oct 2010). Currencies fluctuate in value. Use an online currency converter such as Yahoo finance to get an up to...
Roughly 1.61 as of 16/June/2011. Dont rely on this for more than a month.