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Metric vs. Imperial: Does it really matter?
I want to make it clear that this is not about which system of measurement is “better”. Invariably, discussions about metric vs. imperial devolve into flame wars with zealots from each camp claiming superiority of measurement.
What I want to talk about are the real world advantages and disadvantages of working with each system in a woodworking shop.
I’ve lived in the U.S. my whole life and am accustomed to inches and feet, but converting to metric isn’t difficult and if everything suddenly switched to metric, we would all adapt and it honestly would make no difference to me and would hardly affect my daily life.
Americans like to embrace quirkiness
Let’s start with the obvious: The metric system is the standard worldwide, except for the United States and a couple other places. It’s important to note that just because something is widespread, it is not automatically better. Any Star Wars movie is widespread, easy to consume, and massively popular, but that doesn’t make it better than a small film like, say, last year’s Lady Bird. They both perform the same job of entertaining, just in different ways.
Conversely, just because the U.S. uses a quirky system of measurement shouldn’t make us the hipsters of the world clinging to our vinyl records and trying to convince ourselves about our superior sound quality. (Or our non-mainstream measurements in this case!)
When I was a kid in the 70s, there was a big effort for the U.S. to “go metric”. I think it was the same time this was happening in Canada and elsewhere, but I’m not completely sure. But for whatever reason, probably a lot of reasons, (probably mostly economics) the metric system never really caught on, but more significantly, it never caught on culturally here. Of course it is used exclusively in scientific applications and other important purposes in the U.S. but for the most part, we are perfectly content to go about our days using miles, gallons, tablespoons, inches, feet and even an occasional dash, pinch or a smidge. I’ll be honest though…I really have no idea how big an acre is.
And I think this is really important for non-Americans to understand: Imperial measurements in the U.S. are part of our culture. Most of us fully understand the metric system and agree how simple and logical a base ten system is, but we just love inches anyway! Ridiculing Americans as inferior or “out of touch with the times” for not using the metric system in our day to day lives is culturally disrespectful. It’s like disparaging someone who uses chopsticks because you grew up eating with a fork.
By the same token, most Americans would benefit from being more flexible with measurements and be willing to open up and adapt to metric when needed. Metric isn’t some Illuminati or communist conspiracy designed to tap our precious bodily fluids: it’s just a simplified method for assigning numerical values to things. We are all much better at counting by tens because most of us have ten fingers.
My advice is to learn how to think in the system you are unfamiliar with rather than always try to convert. In other words, begin to develop a mental picture of how long a meter is. For instance, I’ve been using kilometers so long for running that I can easily visualize one kilometer as the distance to the supermarket or 5K as the distance to the community college. I have a mental picture of running 21 kilometers and can assure you that my legs will ache just the same as 13.1 miles! You see, I have no need to convert these to miles to know how far I run. They say you become fluent in a second language when you stop translating everything and just start thinking in that language.
Since I’ve been designing my woodworking plans in both metric and imperial, I’ve become very accustomed to metric measurements and have no trouble thinking in metric, but I’ve also noticed the things that seem to work smoother in each system.
Pros and cons of metric and imperial measurements
When designing projects in Sketchup, metric measurements are a breeze and a vast improvement over inches and feet. They are faster and I make fewer errors.
For instance, what’s half of 438mm? Well, half of 400 is 200 and half of 38 is 19. So 219 millimeters. Pretty basic stuff.
On the other hand, , say I need to cut a 17 ¼” board in half. Quick, what’s half of 17 ¼? Did you get it? Well, it’s 8 and ⅝”. I’m willing to bet most of us would have to think for more than a few seconds.
Using decimeters would be handy
Now in actual usage in the shop, here’s an advantage I see with the imperial system. It has a medium unit called a foot. This is so useful for breaking down measurements into something more tangible. It’s easy for most Americans to wrap our brains around my 6 foot 1 inch height. Or that my shop is 17’ 5” wide. But if I told you that my shop is 209” wide, most Americans would give me a blank look and not be able to really picture how small my space is. The number is too large and needs to be reduced. By having feet, we express a smallish number, then zero it in to just 1 to 12 smaller units, inches.
We even have a bigger unit, the yard, but most of us only use that when it relates to football fields, which themselves have become units of measurements.
In metric, we start with a tiny unit, the millimeter, which is close to a 32nd of an inch. For woodworking purposes, I usually only work to 1/16” tolerances, so the millimeter offers an even greater “standard” of precision.
Then we put ten of those together and move up to the centimeter, the next size chunk. Let’s consider this the mental subdivision similar to the inch unit (even though an inch is about 2.5 cm.)
Then what happens? Metric jumps all the way to the meter or 100 cm. We’ve completely skipped a middle measurement like the foot to help mentally break things up.
But the weird thing is that there IS such a measurement, the decimeter! I have no idea why the decimeter isn’t used, at least for casual spacial awareness.
I’ve learned that metric woodworking plans should be in millimeters only, to remove the decimal point and any potential confusion. My european friends tell me that centimeters are mostly used for clothing measurements and a few other applications. This makes a lot of sense and moving forward I am going to make sure all my metric plans are in millimeters only.
Dealing with big numbers
This leaves us with some big numbers that (at least my brain) has difficulty processing. Somehow a 5 and a half foot long desk is an elegant way to relate a measurement. A 1676 mm desk is accurate and useful, but somehow less graceful and one I would have trouble committing to memory without writing it down.
Wouldn’t it make more sense, spatially, to have a 16.7 decimeter desk in your office? Or better yet, a 16 and three quarter decimeter desktop? Fractions don’t have to be exclusive to imperial measurements. A half a decimeter sounds very practical. At the same time, there is no reason you can’t break down inches into tenths.
In fact, this could be very helpful, especially in woodworking where extremely tiny tolerances aren’t usually necessary. I propose a hybrid tape measure that uses inches and feet, but breaks the inches into tenths. It would make basic shop arithmetic and division much easier. I could quickly cut a 17.2” board into two 8.6” boards.
This is a metric/imperial tape measure:
Like almost all American tapes, It has inch designations and foot designations every twelve inches. So when I pull it out, no matter how long it is, I can quickly take a measurement and spout out, 2’ 9” or whatever for basic communication, but the inches continue the entire length of the tape, so for technical purposes, if my building plans call for 33”, I don’t have to use feet scale at all.
One other thing that is handy, especially for those of us who need glasses to see up close, the half, quarter, eighth, and sixteenth inch divisions use different lengths of lines. This makes them a little easier to read rather than if there were 16 lines all the same length.
In a shop situation, I find myself spending a bit more thinking when using the metric side. Every ten centimeters is marked in red. Remove the zero and these are decimeters, but since nobody is supposed to use decimeters, they indicate centimeters, which also aren’t used in woodworking, but strangely, we need them when using a tape measure otherwise there wouldn’t be enough room for all the millimeter numbers.
So if I need to cut a board 838mm, I need to pull the tape to the red 80 cm mark, then go to the 3 cm mark then count out 8mm. I think it would be handy of there were a 2mm measurement, so I would propose a quintimeter or pentameter, dividing each centimeter into fifths. This would be accurate enough for most woodworking projects and easier to dial in while actually building a project.
Metric isn’t simpler for every situation
Again, the metric system is universal and much more logical and intuitive, easier to design with, and vastly superior when it comes to adding, subtracting, multiplying and dividing and should be the only system used for tech and scientific applications. But I feel that in the shop and in day to day conversational measurements, imperial has the edge. But that might just be for those of us who are more visually oriented.
Having two systems can require a little more work…I know that making two sets of plans for my projects is always a minor hassle. And sometimes we have to get redundant with our tools, but that’s mostly just with wrenches. Buying lumber can be a pain, especially when plywood is sold in metric thicknesses and a ¾” board is not actually ¾”. Having two systems of measurement can cause communication errors that might crop up between the two. But this is mostly hyperbolic.
These problems aren’t really that big a deal in the scope of things. For the most part the two systems seem to coexist in harmony and maybe having both adds a little spice to the world. If you need to convert a measurement, it literally takes a second. Making a small effort to understand and learn both systems can go a long way to keep everybody friendly with each other and make us all smarter in the process.