How Much is a Drop in the Bucket?

It is a term meaning a tiny fraction of the total. But it doesn't neccessarily have to be an unknown tiny fraction. After all, I've got a bucket. Let's pin this down.

I turned a streaming water faucet down to a drip, then counted drips as they filled a tablespoon.

It is possible that drops come in different sizes, but these were natural, gravity-formed water drops. They were nearly identical.

Forty drops fit into the tablespoon.
If the term was "just a drop in the tablespoon", it would mean 1/40th, or 2.5%.

A tablespoon is half of one ounce, and a gallon is 128 ounces, so a gallon is 256 tablespoons by volume.
Therefore "a drop in a gallon" is 1/40th over 256 or 1/10,240th.

Buckets vary in size, but a popular size is 3 gallons.

A drop in a bucket is 1/10,240th over 3, or 1/30,720th

A food service bucket, or hardware store bucket is typically 5 gallons. This is considered to be the largest human-portable size for a bucket.

If this is your idea of a "bucket", a drop in the bucket is 1/51,200.

The term "drop in a bucket" originates before the advent of the 5 gallon plastic bucket, so I'm going to consider the 3 gallon bucket as the default bucket size for this phrase. This makes a big difference.

A drop in the bucket is one thirty-thousand seven hundred and twentieth. That's 0.0032% or 1/30,720th.

To find a drop in a bucket of anything, divide by 30,720.

Examples

The 2013 Federal budget for the USA is $3.5 trillion, so a drop in this bucket is $115,201,823.
(3,539,000,000,000 / 30,720)

The population of the USA is 314 million, so a drop in the bucket is 10,221 people.
(314,000,000 / 30,720)

There are two and a half million deaths per year in the US, so 82 deaths per year in the US are a drop in the bucket. That's a drop in the bucket of people who die in the US every year.
(2,500,000 / 30,720)

Distance across the US, from New York to Los Angeles, is 2,445 miles. A drop in the bucket is 420 feet.
(2,445 x 5,280 / 30,720)

There are 365 days in a year, a drop in the bucket is 17 minutes.
(365 x 24 x 60 / 30,720)

DUI in california is defined as .08% blood alcohol content (BAC). That's 1/1,250th of the blood volume, 0.128 ounces of a five-quart blood supply, or 25 drops in the bucket.