Mashzo

Every other abv calculator multiplies the gravity you lost by 131.25 and hands you a number. HMRC does not, and neither does this one: the alcoholic products technical guide says to multiply the degrees a beer attenuated by a factor from a table the Laboratory of the Government Chemist produced, because the yield of alcohol is not the same at every strength. A beer that fell from 1.048 to 1.011 dropped 37 degrees; the factor for that line is 0.130, and the answer is 4.8%: the shortcut says 4.86%. Three free calculators here work the three sums a brew day makes you do, and each one prints the constant it used and where it came from.

Mashzo is three brewing calculators and the guides that explain the readings behind them, run by Ellul Solutions Ltd. Everything on the site is arithmetic over figures a brewer types in, using constants that are named and linked on the page where they are used.

Who it is for: For the person who brews at home and takes a gravity reading before and after, and for the very small brewer doing the same sums on bigger vessels.

£3 a month