Originally Posted by Stauffbier
I also use BeerTools and BeerSmith and they both match this calculator on my recipes, so I'm comfortable with the calculations it gives me! I used to use TastyBrew as well, which also matched...
Don't know about BeerTools, but Beersmith v 1.40 clearly differentiates between US and Imperial gallons.
Tasty Brew just mentions gallons, and assumes that the only gallon is the US gallon.
Brewheads specifically states that the US gallon is the same as an Imperial gallon, and this is completely wrong.
Google "convert 1 imperial gallon to US gallon" and you will see what I mean.
I have lots of recipes based on imperial measures because I started brewing in England before they went metric. If I were to use Brewheads to calculate my efficiency on one of the old English recipes, it would give me a figure that was about 20% lower than the true efficiency.