Why does my recipe planning software give different figures from what your recipe says.

It’s always difficult chasing other people’s figures, the best approach is to brew it and see the figures you get, rather than seeking to hit specific figures for a recipe which may well have been designed on a system which is different from yours.

There are many factors which will affect how a recipe will come out in planning software, the one which varies from system to system is the mash efficiency, on an all-in-one system like a Grainfather you might get between 80% & 85% but when using a 3 vessel system that might reduce down to say 70%  it’s also not a static value for a system, when you start going up towards the limit of grain that the equipment will hold the efficiency reduces.

Then you have to look at the amount of sugars extracted from an ingredient, this is particularly important if you have created a new malt as the default figures (typically expressed as PPG) will tend to be low, generally you can find a PPG from a Google search for that type of grain, base malts will be around 36-37.

Differences in IBU’s will occur due to similar situations in that the AA% of the hops the recipe was originally designed with aren’t usually available but this figure varies from batch to batch. In practical terms this rarely makes a huge difference to the outcome of a beer, also there a lot of debate about the amount of IBU’s which are imparted in the whirlpool and not all software calculates this the same way, some won’t even count whirlpool additions to the overall bitterness of a beer.

Lastly yeast attenuation, this will usually be somewhere in a percentage, yeast manufacturers will usually include a range, relating to the fermentation of a standard wort, with sufficient nutrients and dissolved oxygen, however there are also factors which will may cause the yeast to operate even higher or lower such as the mash temperature, which some software may take account of, and the addition of simple sugars r enzymes which isn’t usually accounted for in the software.