Having worked for a few years as a baker, converting family-sized recipes to a restaurant-sized recipes from time to time, I can say that the metric system does have an appeal in the simplicity of multiplying by ten, but you get so used to the 16 tablespoons to a cup and 16 cups to a gallon conversion that it isn't hard at all. But while the metric system offers some initial ease of conversion, it comes at a price of rarely getting to measure anything in small whole numbers or even one and half of anything.

Take the following bread recipe in imperial units:

imperial units
4 cups unbleached all-purpose flour
1 tablespoon light brown sugar
1 1/3 cups warm water (110 degrees F/45 degrees C)
1 1/2 teaspoons salt
1 1/2 teaspoons olive oil
1 (.25 ounce) package active dry yeast

1 egg
1 tablespoon water
2 tablespoons cornmeal


Convert this to metric units:
946.35295 ml unbleached all-purpose flour
14.7867648 ml light brown sugar
315.450904 ml warm water (110 degrees F/45 degrees C)
7.39338242 ml salt
7.39338242 ml olive oil
1 package active dry yeast

1 egg (no conversion necessary but the egg should come from a French hen)
14.7867648 ml water
29.5735297 ml cornmeal

Now of course you'd round the metric units up to some reasonable integers so you weren't squinting at the decimal points all day, but since we're going to try to make this recipe even more convenient by using 1 of something, let's do our rounding at the end.

So let's say we're going to slightly enlarge the recipe to use exactly one liter of flour for ease of execution. That isn't such an increase that our dough will be too big for the pan. Since we increased our flour from 0.946 liters to 1.0 liters, we'll increase everything in the recipe by 1/0.946 or 1.057:

1 liter of flourů
1 liter of flour
16.5 ml light brown sugar
333.3 ml water
7.8 ml salt
7.8 ml olive oil
1 package active dry yeast

1 egg
15.625 ml water
31.250 ml cornmeal

Now let's round those numbers to some reasonable integer values since noone wants to measure 7.8 ml:

1 liter of flour
16.5 ml light brown sugar (or round it down to 15)
333.3 ml water
8 ml salt (or round it down to 7.5)
8 ml olive oil (or round it down to 7.5)

1 egg
16 ml water (maybe round this down to 15)
31 ml cornmeal (maybe round this down to 30)

Now here's my point: measuring 8 ml of salt or olive oil is a pain in the arse. Now I expect that what's used is a 5 ml measuring spoon and a 2.5 measuring spoon to get 7.5 ml and call it done. But who's doing more math in the execution phase: the person whose recipe called for 1.5 somethings and they used a 1 something measure and a 0.5 something measure, or the person whose recipe calls for 7.8 or 7.5 ml and they said to themselves, well, that's 2.5 + 5 ml, so I'll use a 5 and a 2.5 measuring spoon. The metric person ends up measuring more stuff in odd little numbers -- no wonder it's called the metric system. A good recipes sees a lot more execution than it does conversion, and I appreciate the simplicity of measuring 1 of this or 2 of those. It's as if someone assigned names to the frequently-used quantities from the metric system: 250 ml, let's call it a cup. 5 ml, let's call it a teaspoon. 2.5 ml, call it half a teaspoon.

Then again, 1 and a third cups is about pi deciliters, so maybe you're onto something there.