Don't put sugar in each bottle. Reserve an amount of beer to bottle and add boiled sugar water to it like you were bottling a whole batch. That way you know you've got it right.

In my example I reserved two gallons to bottle, I figured that 9 1/2 tsp (3T 1/2tsp) was the right amount of sugar.

Here's the numbers you need:

A gallon holds 128 ounces, or ten and three quarters 12oz bottles.

1/2 cup is the total sugar for a five gallon batch, which breaks down to 4.75 teaspoons per gallon.

There are 3 teaspoons in a tablespoon (9.5 tsp = 3 T .5 tsp).

Decide how much beer you want to bottle. Say you want to do one gallon. Clean more bottles than you need (better to have too many than not enough). I'd clean the champagne bottle plus ten 12ozers to be on the safe side. You'll probably have two left over.

Instead of boiling a 1/2 cup of sugar, boil 4 3/4 teaspoons.

My bottling bucket does not have a one gallon mark. Before bottle time put a measured gallon in and mark it. That's why I did two gallons before. It was the smallest marked volume on the bucket.

Start siphoning into the bottle bucket until you have the desired amount, crimp the hose, put the rest into the keg, then bottle the one gallon like you would normally.

I will be doing exactly that with my next batch so I can have some bottles to share with friends who can't come over to the house and have a draft.

I'm fairly terrible at math

That sucks. I do math for fun!