IMO, when you’re dealing with ordinary kitchen recipes (as opposed, say, to mixing pharmaceuticals or explosives) including any decimals at all for units as small as milliliters is ludicrous.

When you pour a cup of vegetable oil from the measuring cup into the mixing bowl, you’re easily going to have a couple ml left in the cup. With less viscous ingredients like water there may be less clinging to the cup, but still a sizable fraction of a milliliter. The average cook probably can’t measure to an accuracy of plus or minus 10 ml, and never needs to.

Providing even one decimal place is pointless, to say nothing of 8 or 16. Make it easy on your readers: round all numbers to the nearest 10 ml, i.e., 236 ml becomes 240.

As for the symbol for milliliters, both ml and mL are accepted. The American NIST recommends L over l, while the international authority, the BIPM, has abstained from declaring a preference. To claim that “everyone else in the world uses a lower case letter L” as the symbol for liter is simply not true. And using mL is not a “typo” either.

This is GQ. It’s important to not confuse individual preferences and idiosyncrasies with standards and correctness.

It’s not a matter of preference. Amidst all the other symbols for units used by the OP, using only lower case letters, the inconsistency was jarring. I have never before seen “L” used for liters, and figured it was wrong.

Biologist here. mL is quite common, and it’s what I’ve been putting in the paper I’m writing. I should really double-check the journal’s guidelines… Pulls out to-do list

3 parts flour to 2 parts sugar, 2 eggs, 1/2 part milk.

Therefore, you have to base your ratios on the one thing that is immutable in size:

The Egg. There is no such thing as a half an egg. Therefore, it is the indivisible atom of cookery.

All the cups, milliters pints,gallons (what are you cooking!) is just a way of shorthanding the amount of stuff you’ll need to have in the recipe to match a given number of eggs.

This, and allow the user to maintain or display customary measurements. Sometimes I want tsp, and sometimes I want grams, but I can never think of an occasion wherein I wanted to measure 10 ml. If the recipe says one cup, I’ll usually use about 235 ml because I’m left handed and the ml scale is on that side of the measuring cup.

Here’s a good one: I can’t buy sticks of butter, and would love to know how many grams to use instead, instead of looking at my printed refrigerator chart and doing the calculation manually.

Cups of common ingredients (e.g., different flours, sugar) auto-converted to grams would be awesome, too.

In most countries, the eggs you buy in grocery stores are graded by size. That doesn’t mean I agree that an egg is an atomic unit. In the U.S., the yield of a large egg is about 46 ml. If you want half an egg, just measure 23 ml (after beating the egg, of course).

You’re using a false degree of precision; you shouldn’t have more than three digits in any calculated value, because you never use more three digits in a conversion factor. (1 gallon = 16 cups is a definition, so it doesn’t limit the precision)

whaaaa? All of the inputs into the formula are exact known/defined quantities. You can extend your calculations to as many decimal places as you wish (it will eventually repeat of course) for as far as you can be bothered to do the calculation.

The formulas are exact for converting figures in US recipes created since 1959. Prior to that date the standard inch in the US was not the international inch (25.4 mm exactly), but 1/36th of 1 metre, or 25.4000508 mm. If the OP wants to be exactly exact, he needs to factor this into his calculations.

Which illustrates the point that the OP’s calcuations are not so much falsely precise as uselessly precise. Cooks do not need the level of precision he offers, and even if they did need it they could not attain it, since kitchen eqipment is incapable of measuring it.

I just recently purchased a scale for weighing spices and the like in the kitchen. It will measure up to 100g in 1/100th of a gram increments. If you lightly blow on the scale you can see the number change. I have played around with measuring small amounts of salt. It is very tedious to get a precise amount of salt within ± .05 g. With measuring cups I would be surprised if I am getting close to 2% accuracy on the markings and would not be surprised if the markings were up to 5% off. Having more than 2 significant figures in recipes is needlessly complicating things.

An inch is 1/36 of a yard, not 1/36 of a meter. An international yard is currently defined as 0.9144 meters. 1/36 of this is exactly 25.4 mm. Prior to 1959 a meter was defined as 39.37 inches, making an inch approximately (not exactly) 25.4000508 mm.

And of course is a completely fatuous level of precision for any purpose outside of a laboratory, and of marginal use within one. Ten-digit precision is like quoting the distance from London to Moscow to the nearest micrometre (or Earth to the Sun to within ten yards or so). You might want that order of accuracy for an atomic clock that needs to be right to within a few milliseconds per year, but not in the kitchen - however exact a science baking might be.

The inch is defined as 2.54 cm exactly. That’s not just rounded; it’s just as correct to say one inch is 2.540000000000000000000000000000 cm.

Every other imperial measurement in the calculation can be described as exact multiples of this number. As noted above:

231 in^3 / gal × 1 gal / 16 cups × (2.54 cm/in)^3 * 1 mL / cm^3 = 3785411764/16000000 or approximately 236.588 mL per cup. And since the exact answer is a fraction, it is a rational number and therefore by definition will eventually terminate in a repeating decimal.

With regard to the unnecessary precision, I see now I should have explained yesterday (when it seemed like TMI) where these paragraphs will appear, which is only in a free spreadsheet that accompanies the cookbook, in a text box headed something like, “In Case You Care.” I prefer to use full precision in these circumstances, even though I know such precision is useless to cooks, for two reasons. The main reason is that it allows users to check my math (or theirs). A secondary reason is that full precision allows users to see at what decimal place, if any, rounding error kicks in.

Knowing the above, should I still reduce the precision to a level that’s practical for cooks?

With regard to ml versus mL, I think mL is certainly acceptable if inconsistent with mm and cm and even km. I prefer mL because it’s so easy, depending on the font, to misread ml as m1 or mi or mI.

Are there any other problems in those paragraphs I should try to solve?

Also, if you can open an Excel 2010 xlsx file I’d be happy to send the spreadsheet to you for you to examine, criticize, and maybe even find a use for. It converts teaspoons, tablespoons, ounces, cups, pints, quarts, gallons, milliliters, deciliters, and liters. Just mail me using “Spreadsheet” as the subject line. I’m pretty sure there is room for improvement and I’d love to know where, so that when we publish the cookbook this BONUS! spreadsheet will be as close to perfect as possible.

True, but recipes seldom specify the size of eggs to be used in them, and when they do, it’s usually “large”, while the most commonly found size at the store is “jumbo”. And even within those size ranges, there’s still some variation.