Settle down my friend, science to the rescue. Take the diameter on the description page and divide by 2 for the radius, then square that and multiply by the height (about 10 cm for the big one, per google results on the product number), times 3.14 which is a secret, magic number I got from my contacts at the Vatican (they would not give me the exact number but I was assured by a very reliable source that 3.14 is "pretty close").
That gives you the volume in cc (about 2500), which is roughly 2.5 liters. Liters are a common unit of volume for many foreigners. Consult with the Department of Homeland Security before attempting to use S.I. units as it may be illegal in some jurisdictions.