where do these numbers come from?

	Statistic	Source
how big is San Francisco?	46 square miles	an encyclopedia
how much does it rain over the whole year?	21.5 inches	national weather service
how many days does it rain during the year?	67	calculated from nws
how much water is in a raindrop?	0.075 ml	a guess
how big is a football field?	100 x 50 yrds	my housemate Gentry
how many people live in San Francisco?	750,000	US Census
how many people live on the Planet?	5.9 billion	a population counter I found on the web
how big is the average glass of wine?	5 oz	a drinking and driving site
how big is the average person?	150 lbs	a guess
how tall is the average person?	5 ft 6 in	a guess
blood alocohol per drink per hr (150lb person)	0.03 (0.10 is DWI)	a drinking and driving site
how much does the average person pee?	300 ml/time	a guess
how much milk does the average cow make?	2,305 gal/yr	the California milk board's web site
how much does a lactating Holstein weigh?	1300 lbs	the California milk board's web site
what is the average depth of the ocean?	12,400 feet	a 1954 physical geology textbook I found in my garage
how much water is there on the Planet?	1.4 million trillion (10^18) metric tons	a 1954 physical geology textbook I found in my garage

if you think some of these values are preposterous, let me know

• Two important things to keep in mind:
  • These calculations only take into account the water that falls on San Francisco when it rains. It doesn't take into account any of the water that falls back into the ocean or the bay or falls on other places
  • These calculations assume that they same ammount of rain falls everywhere in San Francisco. This is definitely not the case.
• Something else to keep in mind is that I'm assuming that the amount someone pees and the amount of milk a cow produces both increase linearily with increasing body size. This is also a guess.

• If you want to figure out how much water falls on something else when it rains (like your head or your backyard or your dog or whatever), the easiest way to do it is to figure out it's area in square centimeters. Then all you have to do is multiply that by the amount it rains (in cm) and divide by 1000 and you'll have the amount of rain that falls on this precious thing in liters.