How much sencha looseleaf for 10 cups?

You should try making one serving first and just multiply by 10. Since Sencha can be tricky to brew correctly, making 10 cups at once could prove very wasteful. Try about 2 level teaspoons for one serving and see how that goes.

--crymad

10 cups of serving ? I don't think it's a good idea to brew that much at the same time. I'd make 5 servings in a teacup that has a volume of 2 cups. For a "light" result, put about 2 spoons of leaves for the 1st serving, and you add one for each next one.

The "spoon" is not a standard unit, I fill it more or less depending on the tea and its freshness.

Kuri