Interestingly enough… the foot, inch, etc. are defined by their relation to the metric system these days. So TECHNICALLY the US does use metric units, we just like to make things harder on ourselves.
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Ala ChatGPT “What if the world standardized on an even worse unit of measurement in 2100”
In the year 2100, using leaves from the American Red Maple tree, the world adopts a whimsical set of measurement units:
- Length Unit - “Maple Leaf”: One “Maple Leaf” is the length of an average Red Maple leaf.
- Area Unit - “Leaf Spread”: One “Leaf Spread” is the area covered by a single, fully spread Red Maple leaf.
- Volume Unit - “Leaf Pile”: One “Leaf Pile” is the volume of a pile made from a specific, standard count of Red Maple leaves.
- Weight Unit - “Leaf Bunch”: One “Leaf Bunch” is the weight of a bunch of Red Maple leaves, tied together, numbering a predetermined amount.
I appreciate the selection of the American Red Maple thus making it more difficult for any other country to have access to a standard leaf to measure with. /S
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There’s an interesting thing that has happened in FTC where we started out with VEX (Imperial), moved to Tetrix (Imperial + Metric) and then subsequent kits have migrated towards metric (REV is metric, Gobilda is Metric) with a brief stop in Actobotics (Imperial). Now another Imperial system has popped up (Robits), but it doesn’t seem like it’s going to set the world on fire.
I think the distinction there is the prevalence of kit in FTC— FRC products have tended until only recently to be isolated components, with the assumption of all structural parts being provided by the team. Since teams needed to source their own structure, and most teams are American, available American materials became the default. In FTC, structure has long since become the domain of kits, so REV went to 15mm extrusion and derived products, and GoBilda went to various metric sizes of channel/beams that were improvements on/based on the old Actobotics line.
In addition, how long a team lasts tends to be very different–in FRC a team will generally either fold within a few years or last a long while. In FTC, a huge chunk of the team population is living on a 4-ish year time limit, and while their parts may be donated or sold to another team when they fold, it’s just as likely a new team decides to purchase parts from whoever the currently perceived best vendor is, so changeover happens faster overall.
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Also our next moon landing will be using metric (as NASA has been ~99%¹ metric since about 2007).
¹ units are translated to Imperial for press releases, etc
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If you don’t know what happened in 2007*, don’t ask. 
*well, really, 1999, but that’s the speed of government funded programs
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it started in 1990, they just achieved ‘‘extra incentive’’ in 1999 (and it still took 8 more years to finish, but big ships turn slowly)
yeah, 1cm = 2.54 inches…
2.54… now where have I heard that before
its obvious! the cheezy poofs created the imperial system!
Edit: 1 inch = 2.54 centimeters. Insert garfield monday meme here
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Ahem.
Mighty big centimeter you got there, was your ruler made in your own shop to your own standards?
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Actually, it was a Swede. Carl Johansson, creator of Gauge blocks (Jo Blocks). He split the difference between U.S. and U.K. inches (because they weren’t the same!)
From Wikipedia:
In the early 20th century, the U.S. inch was effectively defined as 25.4000508 mm (with a reference temperature of 68 °F (20 °C)) and the U.K. inch at 25.399977 mm (with a reference temperature of 62 °F (17 °C)). When Johansson started manufacturing gauge blocks in inch sizes in 1912, Johansson’s compromise was to manufacture gauge blocks with a nominal size of 25.4mm, with a reference temperature of 20 °C (68 °F), accurate to within a few parts per million of both official definitions. Because Johansson’s blocks were so popular, his blocks became the de facto standard for manufacturers internationally, with other manufacturers of gauge blocks following Johansson’s definition by producing blocks designed to be equivalent to his.
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Measure once, cut twice!
im too tired for this 
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I actually liked that feature. It felt like an intentional “Are you sure you want to do this?” 2nd step confirmation.
My favorite fact here is that the US has secretly been one layer away from metric since 1959 when the imperial yard was redefined to be based ON THE METER.
For the past 10 years, I have start every class with the same speech and same assignment Day 1. “I will only use my pulpit of power to convince you of 2 things, 1. We should be on the metric system (except for pressure) 2. We should abolish the Penny, it’s a scourge on our society. If you don’t like something write your congress person.”
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Good video from Joe Scott on the “many times the US tried to go metric”. Unfortunately its only on Nebula.
I find the metric system more intuitive from a math point of view. But I don’t have a good “feel” for it in day-to-day use like I do with Imperial.
Just think of converting as fun math practice! 
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There’s a good video from SNL with Nate Bargatze as George Washington on measurements in the US. “We are free men! And we will be free to measure liquids in liters and milliliters… but not all liquids, only soda, wine and alcohol. For milk and paint we will use gallons, pints and quarts, god-willing.”
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605, 608, 6000, 6201.
The only bearings you’ll ever need. ™*
*If they come in both round and hex bore options, and with or without flanges.
I think in millimeters and convert to inches when necessary – dual dimensioning is a great option when making drawings from your CAD models.
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Yeah, that policy is on the books to make the bureaucrats feel fashionable.
In practice, every project that I know of has a waiver against it, so that we can use normal sizes.
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If it’s any consolation, WPILib uses metric.
Maybe for hardware, but the flight software I’ve worked on is in metric. It’s easier to implement the math that way.
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should be “those who use the metric system, and those who have used the metric system to land on the moon.”
seriously. All the math we did to go to the moon was done in metric, and only converted to imperial units for display to the astronauts.