So which is better; random objects or water? Do you prefer to measure with sticks and limbs, or with increasingly small divisions of ten? Sticks and limbs refer to the yards, rods, hands and feet, of course. Even the inch comes from the Latin uncia, which means “one twelfth-part,” meaning one twelfth of a foot (whose foot?).

You might wonder where I’m going with water and increasingly small divisions of ten, and you’re right to be curious. The metric system has a much more interesting history than does the imperial system, but perhaps being Canadian, I am biased. The metre comes from the length of rope required to reciprocate a pendulum one direction each second. Base ten is involved because every unit in the metric system can be created by multiplying or dividing by ten. There are ten millimeters in a centimetre. There are ten centimetres in a decimetre. There are ten decimetres in a metre. You get the picture.

Water comes into play with the metric system, because it was used to define volume and mass. The French developers of the metric system took one cubic metre, filled it up with water, and called it one metric tonne. A metric tonne consists of a thousand litres. A litre weighs exactly one kilogram. There are a thousand grams in one kilograms. A gram is exactly one millilitre. One millilitre is exactly one cubic centimetre. If you’re not familiar with the metric system, this paragraph is just a lot of oddly spelled words. But trust me, its simplicity is genius.

So what is better when you’re arguing imperial versus metric system? Well, in everyday life, the metric system is much easier to grasp and use. For example, when I blend my protein shake, I put the shaker bottle on my kitchen scale and measure until I’m at 300 grams. 300 grams is 300 millilitres, which is exactly what the recipe calls for. To be honest, I have absolutely no idea how much a fluid ounce weighs, although oddly enough, I’ve heard it doesn’t weigh exactly an ounce.

But what system is better for hydraulics? To be honest, it really doesn’t matter. The only advantage I can think of with the metric system is some of the simple math, like for flow. Metric flow is simply displacement in cubic centimetres x rpm, and divided by 1000 to get litres per minute. The imperial system uses a division of 231 to convert from cubic inches per minute to gallons per minute, but to be honest, I’ve had every imperial hydraulic formula memorized for years. No simple base ten is required at this point.

Is a 50-mm cylinder better than a 2-in. bore cylinder? Absolutely not. Does a 1-in. tube flow any differently than a 25mm tube? Hardly. The only real difference is where they’re used. In some parts of Europe and Asia, metric is used for plumbing, porting, cylinders and pumps, etc. But in other parts of Europe and in North America, the imperial standard is used for those same components. The unfortunate reality is they are not interchangeable. I work for a NFPA cylinder manufacturer, and we get semi-frequent requests for metric cylinders. The material to manufacture them in North America is hard to come by, so we decline.

Now what is fortunate, is there are manufacturers who have recognized the disparity, and make products for every market (thank you Bosch Rexroth). Their A10V pumps are available with either imperial or metric shafts, flanges and ports (although all displacements are in metric). Rexroth is smart enough to get their hands in every market, but they might not be helping the bigger problem.

We need to pick a single standard and stick with it. Auto manufacturers are close, and most cars these days are to the metric standard. Having one unit of measurement means one set of tools, one series of molds and dies for machinery and one set of measurement devices. The North American manufacturing industry has a better chance of export success when they can ship their machinery in metric, as well. Other than the expense of the conversion, I see no downside. The switch will be inevitable, but I’m a terrible proponent, because I still don’t know how many centimetres are in my 6 ft 1 in. height.