cooking measures

Hal Canary
https://halcanary.org/vv/2008/09/07/731/
#food

I have no idea how I got to thinking about cooking measures, but it's a topic that always confused me. How many teaspoons in a fluid ounce?

You only need to remember half-a-dozen rules

  1. Three teaspoons in a tablespoon.
  2. Two tablespoons in a fluid ounce.
  3. Sixteen ounces is a pound.
  4. A pint (of water) is a pound.
  5. A cup is half a pint.
  6. Two pints is a quarter gallon is a quart.

Numbers 3-6 I have down. I always forget 1 and 2.

And for metric conversions you need to know two definitions:

  1. 1 inch is defined to be 2.54 centimeters.
  2. 1 US gallon is defined to be 231 cubic inches

US Customary system of measure.

tsp.	Tbsp.	fl. oz.	cup	pint	quart	gallon	exactly
1	1/3	1/6	1/48	1/96	1/192	1/768	= 4.92892159375 mL
3	1	1/2	1/16	1/32	1/64	1/256	= 14.78676478125 mL
6	2	1	1/8	1/16	1/32	1/128	= 29.5735295625 mL
48	16	8	1	1/2	1/4	1/16	= 236.5882365 mL
96	32	16	2	1	1/2	1/8	= 473.176473 mL
192	64	32	4	2	1	1/4	= 946.352946 mL
768	256	128	16	8	4	1	= 3785.411784 mL

These are the definitions I grew up with. Since 1inch := 2.54cm (by definition), 1 cubic inch = 16.387064 mL. Since 1 US gallon := 231 inch^3 (by definition), 1 US gallon = 3785.411784 mL = 3.785411784 L, exactly.

The teaspoon is totally out of place here. Whose idea was it to introduce a THREE into this system? Why not use fluid drams, which are 1/8 fl.oz? Too late now, I guess.

Here are three different attempts to shoehorn the customary units of cup, tablespoon, and teaspoon into the metric system. None of them works well, since you end up with too many improper fractions like 50/3, 25/2, or 25/6.

Metric System (Canada, New Zealand -> 1Tbsp=15mL, 1cup=250mL)

mL	tsp.	Tbsp.	cup	Liter
1	1/5	1/15	1/250	1/1000
5	1	1/3	1/50	1/200
15	3	1	3/50	3/200
250	50	50/3	1	1/4
1000	200	200/3	4	1

Metric System (Austrailia -> 1Tbsp=20mL, 1cup=250mL)

mL	tsp.	Tbsp.	cup	Liter
1	1/5	1/20	1/250	1/1000
5	1	1/4	1/50	1/200
20	4	1	2/25	1/50
250	50	12.5	1	1/4
1000	200	50	4	1

Metric System (US FDA -> 1Tbsp=15m, 1cup=240mL)

mL	tsp.	Tbsp.	cup	Liter
1	1/5	1/15	1/240	1/1000
5	1	1/3	1/48	1/200
15	3	1	1/16	3/200
240	48	16	1	6/25
1000	200	200/3	25/6	1

Since SI simply doesn't define these units, why use them at all? Seems tto confusing in a global economy.