Okay, this is a bit of an oddball question.

I've two characters who go up to the roof of their four-story tall apartment building to build a snowman, because the snow on the street is all slushy and gross. I want one of the characters, who is highly analytical and logical, to calculate how big of a snowman they can theoretically make, based on the volume of snow on the roof.

I'm utter rubbish with math, but looking at a not-to-scale map of the apartment, I'm guessing the square footage of the roof would be about 900 square feet. (It's in London, but I haven't converted all the numbers yet. Do they use square meters for house sizing in the UK?) The snow is currently about 5" deep, but this can be changed, if need be.

I've written that they could, in theory, build a snowman with a base that's 2 meters in diameter and 4 1/2 meters tall, but that's just random numbers that sound good, based on typical snowman ratios. I've no idea if it works with the size of the roof and depth of snow. Basically, I want the proposed snowman to be ridiculously huge, so the other character can veto it in favor of a normal snowman. So if the roof is 900 square feet, how deep does the snow need to be in order to make a giant snowman? (Note: The snow depth and the size of the snowman are variables that can be changed, but the roof size needs to stay at 900 square feet.)

Please, please don't respond by telling me how to do the calculations myself. I have dyscalculia, so math is my Moriarty. Someday, we'll die with our hands wrapped around each other's throats.