Oh Metric. Like sunscreen/exercise/calling your mom, we all know you’re the right thing to do, and yet, we resist. I’m speaking as an American of course. The last holdout to joining team worldwide measurement system. (Well actually, three way tie with Myanmar and Liberia)

When Damein and I started putting real time into Revision, we had to decide which system of units we would use to build CAD models in. The decision wasn’t obvious. In school, I mostly used inches and thousandths of an inch to spec out designs. Same for my first few jobs. But I always had a soft spot for the relentless logic of metric. We opted to abandon our country’s standard and fully adopt metric. 

Since then, I’ve found metric to be a delightfully useful system. I’ve tried to bring it into my life in every way I can. Here’s why it wins the day (it’s not the same things you’ve been told before).

Here’s what you already know about metric: it’s based on meters and you can divide things by 10s to reach other units. That all checks out, but it’s not metric’s superpower. Here’s where things get useful:

Humans are inherently bad at judging area. Look at a table and the number of square inches won’t spring to mind. Humans are even worse at judging volume. Is a 10,000-gallon room big or small? Adding a dimension makes things more abstract and harder to manage in our ape brains.

With imperial, each new dimension to be measured get’s its own unit mostly free of the base unit. The only way to get a good sense of ounces is to be a baker and use it every day. With metric, a good sense of centimeters equates to a good sense of milliliters. You can borrow the skill over and proceed with a decent guess. This is metric’s superpower.

Metric’s Secret Power

Here’s what metric can do: I see a carton of milk that appears to be 10 cm by 10 cm by 22 cm. I can do the mental math and know that it holds 2.2 liters by measuring it with my eyes.

If you see a carton of liquid that’s 2 inches by 2 inches by 10 inches, how many gallons does it hold? I’ll tell you the answer: (2X2X10)/231. That’s right, someone decided there are exactly 231 cubic inches in a gallon so you get to throw that big ass prime number into your mental arithmetic. If you’re not a mental math genius, you can’t do it. The only option is to learn the gallon as a unit itself and hope that knowledge sticks. Someone might point out that if you use cubic inches determining the volume is rather easy. That’s true, but I’ve never seen a measuring cup with cubic inches on it. That’s not how imperial works.

I’ve found that my perception of volume has actually grown stronger now that I’ve been using metric for about a year. The American system I grew up with left me hanging with a long list of unrelated systems. I have to guess based on how many gallons it ‘seems’ like based on my mental estimation of a gallon as a standalone unit. Metric is so interconnected, it helps you perceive the logic and make better guesses in all kinds of situations.

For many people, this doesn’t really matter. But for a designer, or anyone who measures, it does. I spend all day making estimates and weighing tradeoffs between geometric changes to a design. It’s paid off tenfold to have a system that allows my mind to make decent estimations on the fly.