I like experimenting with my own brew recipes. I can measure OG with a hydrometer and FG after fermentation is complete, but is there a formula that I can use to calculate an expected FG before I brew the recipe?
What I normally have done is to find a similar published recipe with a similar OG and guess my FG might approximate that.
P.S. I do my own calculations in excel.
Thanks in advance for your advice.
An average yeast under average conditions will give you approximately 75% apparent attenuation. Do you agree? Then do this:
In Excel, this looks kind of like:
Hit enter in A5 and it should spit out the expected result: 1.015.
You can toy around with percentages and decimals instead of dividing by 4, but this will give you a swaggy ballpark result.
Others are of course correct when they say there are many variables, the primary one being yeast strain, followed by grist, mash time, mash temperature. I keep close track of average attenuation for every yeast strain because I know it makes the biggest difference of all.