How to predict ABV in cider?

Question

I am new to cider brewing (my first batch has just started fermenting). As I'm new and just want to trial the process before getting into something more involved, I used store bought juice (no additives etc).

I got myself a hydrometer, and have measured the OG (1.049) and understand that I will need to measure the FG to calculate the final ABV.

My question is this: if I need the FG to calculate the ABV, how does one predict the final outcome? Is the OG any indication of where you'll end up?

I didn't add any sugar to my batch, so worried the ABV might be too low?

Also, when I start my second batch, I'd like to aim for around 10%, so unsure how to work out how much sugar I should add to reach that volume.

Thanks in advance!

Answer 1

To add to the other answers, what you are looking for to determine how much sugar to add to your must (juice) is a Chaptalization calculator.

Link to calculator here

What this calculator tells you is that at 1.049 SG, if the must ferments to near complete dryness, you would have an ABV of 6.5%. By increasing the SG to 1.075, if the must ferments to near complete dryness you would have an ABV of 10%. The 9 ounces of sugar you would need to add has a potential ABV of 3.5% when dissolved into 1 gallon of liquid. So the current 6.5% & potential 3.5% add up to 10%.

You may want to ferment to complete dryness & then back-sweeten a bit depending on whether you desire a sweet cider or not & also considering whether you want some sugar remaining at bottling to produce carbonation.

Answer 2

you can predict ABV by using the yield calculation, Safcider gives 1% of ABV for 16.3g/l

1049 ~ 135 g/l 
therefore 
135/16.3 => 8.2% ABV

Or you can get more complex by looking through these equations, but that is overkill for a quick homebrew, unless like me you are a bit of a science/maths geek: http://realbeer.com/spencer/attenuation.html