Last I heard Blackrock and Mangrove Jacks kits were using

Mauri 514 yeast in their kits (follow the link), If I were making a kit in Oz or NZ its probably the yeast I would reach for first.

Roughly to calculate the ABV we take the change in gravity and divide it by 7.5. The easy way is to treat the 3 places after the decimal as whole numbers (ie 1.050 would be called 50 "points). If a 1.050 wort was fermented down to 1.010 we would say the change was 40 points. The ABV would be 40/7.5=5.33%. It’s the CHANGE in gravity that matters.

Pretty obviously if you add more fermentable sugars (brewers call everything other than water/moisture Solids) your OG goes up. The more of those solids that are fermentable the higher the alcohol content. The more of the solids that are unfermentable the higher the FG and the lower the alcohol content... Within the alcohol limits of the yeast.

If you added 1kg of Lactose your OG and FG would go up by the same amount but the ABV wouldn’t go up at all.

If you want to have a play around with the numbers (even if you use a calculator it’s good to know what it’s doing), the basic equation you need is -

Mass Solids = Volume * SG * oP

Plato (oP) is the % weight of solids in a given mass of wort, to get from SG to oP (approximately) we use -

SG = (4*oP)/1000 = 1

So a 1.050 wort would be 12.5oP or 12.5 % solids

Volume of wort times its density gives you the mass of wort so if you had 23L of wort at 1.050 it would have a mass (OK weigh) of 24.15kg, 12.5% of that being ~3.02kg (solids)

A couple of other handy bits of information

LME is around 80% Solids; a 1.7kg kit contains ~1.36kg of solids and around 65% fermentable.

Dry Malt Extract is ~98% Solids and around 65% Fermentable.

Sugar (Sucrose) is 100% Solids and 100% fermentable.

Dextrose is 91% Solids (9% moisture) the solids are 100% fermentable.

Maltodextrin and Lactose are pretty much 95% (can be a pretty wide rang from 2-9%) solids and 0% fermentable.

Honey is around 80% solids and all of it is fermentable (well except for some very nice smelling/tasting bits and pieces <1%).

Tinkering with the equations lets you predict pretty accurately what both your OG and FG and the resulting ABV will be.

Sticking the equations in a spreadsheet and using "Goal Seek" makes it pretty easy to manipulate.

Yes brewing is a science.

Mark