Konrad its hard to measure. One method is boil off the alcohol (and some water), replace all the liquid lost, then measure SG. See link below for an article on it. I never tried it myself, I usually just drink a glass and wait an hour :-)

Scott

You may also find a calculation to measure with a hydrometer and a refractometer and the difference will tell you. I know of one like that for beer but not wine, should be close.

Then I guessed right, it's around 4%, when my wife drank two
sips and was already tipsy! lol [she can't handle anything!]

My wife is the same way. A couple of sips of an adult beverage at a restaurant and she feels tipsy.

Konrad, trade me some of your ale for peaches. If I can get my wife to drink it maybe I can get her clothes off easier. LOL.

If it was wort/beer (it's not so this isn't accurate either) that had a SG of 1.051 and measured 9° when finished BeerSmith corrects that to 1.026 FG. A potential about 2.5%-3% (I really don't like my hydrometer's potential scale so I don't trust that to be perfect, broke the one I did like). So about 3%-3.5%ABV.

The 3.5% sounds about right for sweet cider that wasn't bumped with a sugar and assuming the 1.026FG estimation is near correct.
About 5%-6% for a dry cider.

Without a hydrometer rely on taste, balancing that with other flavors (alcohol is low so that's not a factor). Hard to do without a hydrometer to give you the experience.
1.026 sounds sweet in an apple. Is it?
Granted I use honey which tastes sweet even when it's not but I have some 2 year old Cyser that is 1.010/13% and it's too sweet for my sweet tooth tastes. 1.010/16% wasn't too sweet.
Sour cherry pie wine @1.026 is sweet but the sour balances it.
Under 1.000 is extremely distasteful to me. Sour cherry wine that went to .990 would turn my face into a black hole. I aged that stuff 10 years and while it lost some sour it was never enough by the time it was oxidized.

Really without a hydrometer and a SG-FG to go on it's a guessing game. On beer and wine forums when someone comes on forgetting to take a SG they don't get time wasted on them because at that point it's all a guessing game even with all the methods and formulas.
If you want to know, get a hydrometer and don't forget to take the initial reading next time.
Until then if it's good drink it. If not age it until you need the space.

Will the hydrometer get me the correct reading after the brew when there is alcohol in it?....I have one somewhere but haven't used it in years...usually my tongue is the hydro/refractometer.