Your tongue has a sweet spot
Most people like soup near 1 percent salt. That is close to the salt level in our own body. Much lower tastes flat. Much higher tastes harsh.
One tablespoon, one cup
One tablespoon of soy sauce holds about 2.5 g of salt. So it seasons about 250 ml of soup to 1 percent. This rule works for any broth.
Dips and stews are different
A dip only coats the food. It can be twice as strong. A stew reduces as it cooks. So start it weaker than you want.
Shunta says:
I used to add soy sauce until it tasted right. Now I measure first. I rarely fix it later.
