I have a litre of olive oil but don't know how much it weight. Basically, it's easy - multiply the oil density by its volume and you will have weight.
So I've decided to make a calculator about this (see below).
Then set its volume as you like it - litres, cubic metres, even length, width and height. Then it will calculate weight.
Density set in grams per cubic centimeter in the reference book. If there is no some matter in reference book somehow you can always add it if you are registered user.