quoting myself (makes me senile, right?)
It's all easier if you use excel or another converter...
1st, convert gallons to liters (because liters are about the same as kilograms)
1/1000000 of a Kg is a mg
1cc=1mL=1g=1000mg aqueous liquids (again, it's close)
There are about 20 drops per cc from most eye-droppers
when you have a liquid solution (ammonia, ferts etc.), you divide your desired weight of whatever by the %whatever is in the solution
for example, you want 5ppm ammonia in a 100L tank, 100L=100Kg so you need 500mg ammonia. If your foam-free cleaning solution is made of water & 10% ammonia, you need 500mg/10%=5000mg solution.
5000mg=5mL
(originally posted here:
at AA)
edit - thanks eyeman, the link you reference is a bit more detailed (I forgot abt that one :: takes anti-senility pill :

.