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Or more, depending on how long you leave it on the radiator.
A mate of mine is a brewer (Wiper and True) and he started off doing bottle conditioned beers. He always marked them up as something around 4.5 abv, but his beer was notorious for giving you tunnel vision after about 3 bottles. I think his abv callipers were £3 off eBay or something. I assume stated abv can never be that accurate anyway, so don't know why they bother with a decimal point.
AlexD-
OTOH if it's that far off the excise man may take a close interest...
(Entertainingly (OK, I'm easily entertained), historically the authorities didn't give a crap as to whether your beer was safe to drink, just whether you'd paid the correct amount of tax on the malt used. The consequence was watered-down beer pepped up with (amongst others) caramel, liquorice, spices, and strychnine, all to give the resulting brew the same mouthfeel and pep as actual beer. It was only in the 19th century that the public health implications of beer adulteration became enough of a concern to government for it to be banned. /csb)
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Actually if you know the original gravity (sugar content) of a liquid before and after fermentation then even rudimentary calculations using equipment from wilkos can be very accurate. Even measuring the refractive index of a fermented solution can give a fairly accurate (0.2+/-) reading.
Thrustvector
matteroftaste
Entertainingly fresh orange juice can be up to 0.5% abv