On Units of Measure

This is possibly the dorkiest thing I’ve ever written.

Measuring cups and spoons

In some respects Canadian culture is a grab-bag of European and American attributes.  Nowhere is this mash-up more complicated than the blend of metric and US units that every Canadian uses in daily life.

I estimate that every day at work I do about 57 unit conversions in my head.  I know, for instance, that 8 fluid ounces is a good portion of soup for an individual, and if I need to make soup for 10 people, I’ll need 80 oz.  But the can of tomatoes that I will turn into soup is labelled 2.84 L.  80 oz is 10 cups, which is 2 1/2 quarts, which is roughly 2.5 L, so one can of tomatoes will suffice for the job at hand.

US v. Imperial Units

Canadians often say that the Americans use Imperial units, but this isn’t true.  The British Imperial System was not standardized until 1824, well after the Americans had won their independence.  The Americans use a system called the US customary measure, which uses a collection of measures from the imperial system before its standardization.  As such, while the nomenclature for the British and American systems is almost identical, many of the measurements are different.  Both measure volume in gallons, for instance, but the imperial gallon is 4.54609 L, while the US gallon is about 3.785 L.

When Canadians make reference to fluid ounces, or gallons, we are almost always referring to US customary units, not British Imperial units.  One notable exception is in ordering “pints” at a bar.  First of all, very, very few establishments in Canada offer true pints.  In both the imperial and US customary systems, one pint is half a quart.  However the two systems define quarts differently.  In the imperial systems a quart is 40 fluid imperial ounces, so a British pint is 20 ounces x 28.41… mL/oz = 586 mL.    In the US system a pint is 32 fluid US ounces, which corresponds to 473 mL. Unfortunately we don’t take the term “pint” as seriously here in North America as they do in the UK, so when you order “a pint of beer” you are basically just asking for draft beer, and the establishment can serve you your drink in whatever glass they want.  (Find out why this is a problem here.)


Volume v. Mass Measurement

Volumetric measurement of solid pantry items like flour and butter is a hallmark of traditional North American cooking.  After Lisa and I hosted an Austrian culinary student for a summer, he went home with a set of measuring cups just so that he could use the many recipes he wrote down while he was here.  Volumetric measurement of solid ingredients does not exist in European kitchens: they weigh solid ingredients with a scale.

The explanation I have heard for the origin of volumetric measurement in North America is that on the frontier it was more practical to carry around a set of measuring cups and spoons than a set of weights and scales.  This kind of makes sense to me when I think about a pioneer family in Alberta, but I don’t see how the practice could have spread back east to the places that were settled for hundreds of years before that, like New York and Quebec.

Volumetric Measurement as a Source of Inconsistency.  A cup of flour can weigh anywhere between 4 and 6 ounces depending on the wheat, grind, brand, packaging, and whether or not it has been sifted.  Sugar and salt have similarly different masses per unit of volume depending on brand and coarseness.  These ingredients should always be weighed.  An electronic scale accurate to 1 gram is an essential kitchen tool in my mind…


Metric v. US

The metric system is often touted as “more accurate” than US customary measure.

Accuracy v. Precision.  The best way to explain the difference between accuracy and precision is to imagine a target with concentric rings surrounding a bull’s-eye.  The shooter is aiming for the bull’s-eye.  Accuracy would be defined as the proximity of any individual shot to the the bull’s-eye.  Precision would be a measure of how tight the shooter’s groupings are.  So if the shooter never hits the bull’s-eye, but has a very tight grouping of several shots, we would say that he is precise, but not accurate.

With units of measure, the smaller the unit the more precise it is.  If you have two rulers, and one only marks centimeters, while the other marks millimeters, the latter is more precise, but not necessarily more accurate.

But strictly speaking grams are not a more precise unit that ounces.  For instance 50 g can be represented as 1.7367 oz.  Humans find it much, much easier to deal in whole numbers, so it is easier to remember the number 50 than the number 1.7367, even though they represent equivalent measures.

The beauty of US customary measures.

Will Jim and Peter be devoured by the killer ants? Will Psycrow destroy the Earth? Will the U.S. ever adopt the Metric system?

-from an episode of Earthworm Jim

While there is no doubt that the metric system is more intuitive, easier to learn, and superior in ease of computation (read more here) the US system has its benefits, especially in the kitchen.

For instance: in many cases the US system produces small, whole numbers that are easy to remember and perform arithmetic on.  An appetizer-sized portion of protein is 3 oz.  An entrée-sized portion of protein is 6-10 oz, depending on the context of the course and what is being served.  A typical large egg weighs about 2 oz.

I often write about the power of cooking with ratios instead of conventional recipes, and working in ounces makes ratio arithmetic a breeze.

On a more abstract level, the US system also has more character and soul than the metric system.  Inches, miles, horsepower, and degrees Fahrenheit all have a special resonance to North American ears.  They’re quaint.  It’s kind of like when the NHL changed the Campbell and the Wales Conferences to the Western and Eastern Conferences.  Of course this is more intuitive and easier for outsiders to understand, but the NHL gave up a little bit of its history and character in the process.


The Positively Baffling Units of the Canadian Professional Kitchen

Temperature. Canadians measure ambient temperatures in degrees Celsius, but oven temperatures in Fahrenheit.  For instance: I know that room temperature is 20°C, and a hot day is 30°C, but most quick breads are baked in a 350°F oven.  I do a lot of catering in private homes, and if the homeowner has a fancy oven from Europe that displays temperature in Celsius, I am completely lost.  The temperatures for sugar work are always in Fahrenheit.  The only temperatures that I can comfortably move between Celsius and Fahrenheit are the finishing temperatures for meat (a medium rare roast beef is 55°C and 130°F).

Distance. Personal height and short distances are in American feet and inches.  Long distances, especially distances between cities, are in metric kilometers.  Track events are in metric, though when I was growing up we had to run a 1.6 km race (a mile).  In the kitchen, both systems are used, but I would argue that the American predominates.  Classic knifework is explained in American units:

  • small dice: 1/4″ x 1/4″
  • julienne: 1/8″ x 1/8″ x 2-3″
  • brunoise: 1/16″ x 1/16″

Understanding long Canadian distances in miles is a distinctly prairie gift, due entirely to the Dominion Land Survey.  (Most of Canada west of Winnipeg is surveyed in American miles. The Wikipedia article on the DLS explains why, and is also just really, really fascinating.  You should read it before you eat at RGE RD.  Just kidding.)

Speed. For people under the age of fifty, speed is always in kilometers per hour.  Sometimes familiar phrases from the States (miles per hour, miles per gallon) will sneak into our vocabulary, even though we are actually referring to the metric equivalent.  Obviously this measure has little use in the kitchen; I just included it for the sake of completeness.

Weight. This is an interesting one.  I would say that most Canadians deal exclusively in American pounds (notably: baby birth weights and personal weights), with the following exceptions: ordering meat at a deli, or purchasing small quantities of marijuana.  In the professional kitchen pounds and kilos and ounces and grams are all used frequently.  In most of the restaurants I’ve worked in, for some reason meat is ordered from distributors by the kilo, whereas fish is ordered by the pound.  Conventions for sizing seafood like shrimp and scallops uses pounds.

Volume.  This is one where we are so confused that we are actually comfortable in both metric and American.  From millilitres to fluid ounces and cups and quarts and litres and gallons.  Alcohol is always ordered by the US fluid ounce.  A “2-6” is a 750 mL bottle of liquor, which is about 26 fl. oz.

Alcohol Content. In Canada all alcoholic beverages must be labelled with the percent alcohol by volume (ABV).  In the states some regions use or used to use percent alcohol by weight (ABW).  Because alcohol has a different density than water, these two measures are not equal; the ABV measure will always be a higher number than ABW.  I’ve heard that after Prohibition was repealed, many producers in the states provided the ABW system, with its lower numbers, to make the drinks appear temperate.

The other common measurement that appears occasionally in Canada is the proof system.  The American proof number is double the ABV.  So 90 proof bourbon is 45% ABV.


Old Timey Units

I love you a bushel and a peck
A bushel and a peck and a hug around the neck.

-Doris Day


I leave you with the hilariously precise definitions of some antiquated units.

  • drop = 1/60 tsp
  • dash = 1/8 tsp
  • jigger = 3 tbsp
  • peck = 2 gallons
  • bushel = 4 pecks = 8 gallons