Very roughly

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Thought these might be useful. The below are approximations of brewing calculations which might not be 100% accurate but are near enough.

So very roughly :-

To calculate the ABV% of beer you get the gravity points of OG and FG, divide them by 10, take the FG from the OG and add 1. As an example if you make a beer with an OG of 1.042 and an FG of 1.012, you get :-

42/10 = 4.2, 12/10 = 1.2
4.2-1.2 = 3
3+1 = 4

So its 4.0% ABV. A calculator gives you 3.94% ABV. As you get higher OG the calculation gets rougher.

To get gravity points from brix multiply the brix by 4 and that's your gravity points. Useful if you've got a refractometer that just gives brix. Example - your wort is 9 brix, 9 X 4 = 36 gravity points or 1.036 SG. Calculator gives 1.0359. Reasonably accurate right into wine territory although it undershoots a bit when you get above about 1.080. This only works pre-fermentation.

2.5g of sugar gives 1 gravity point in 1 litre approximately. So if you need 5 points in 20 litres you need 2.5 X 5 X 20 = 250 grams of sugar. If you need 20 points in 20 litres you've done something wrong :laugh8:.
 

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