How many grams in a Campden tablet?

I would appreciate it if someone could weigh for me, in grams, a campden tablet (my scale has finer devisions with grams than oz). I bought some metabisulfite powder and I want to use it to treat my brewing water to remove chlorine. The instruction on the package are geared toward sanitizing for wine makers. People report to use half a tablet, or that a tablet treats 20 gal. etc., but how big is a tablet?

Thanks in advance!

Direct from the wiki:

Campden tablets typically weigh 0.44 g each and 10 of these are equivalent to one level teaspoon of sodium metabisulphite.

Some more information on tablets and corresponding powders.

The Various Uses of Campden Tablets «

Thanks. I think my supply will last a loooong time.

They are not all the same. Some are potassium metabisulfite and some are sodium metabisulfite. The Campden tabs I have are sodium metabisulfite, and they weigh .60 grams each. I weighed using a scale that is accurate to .01 grams (Acculab VI-400).

You can buy potassium or sodium metabisulfite in powder form if you want to make precise measurements, although Campden tablets are cheap and easy to use and a little excess sulfur dioxide won't hurt anything.