I want to say:
He weighs 100 kilograms, which is too much.
But I am confused as to which relative pronoun to use, and why. The problem is that I don’t think the pronoun (der, die, das) is actually describing Kilo.
Er wiegt 100 Kilo, die zu viel sind.
That doesn’t sound right to me, as I don’t want to describe the word Kilo itself.
Er wiegt 100 Kilo, die zu viel ist
That also doesn’t sound right due to using ist with the plural.