Oh yes, then you need to figure out if 7/16 is bigger or smaller than 3/4. No, thanks.

You can easily divide by 2 and 4 in metric, because guess what, you just add a decimal point to your measure and 10cm/4 is 2.5cm and not some crazy fraction or weird unit and the math is not harder if you're dealing with 10m as opposed to 10cm.

10cm/3 is 3.3cm or whatever the precision of your tools is. It's the same "problem" (it isn't) with dividing 1ft in 5 for example. You go by the tolerance of your tools

It's a lot easier to do things when you don't have to go "okay, what's the conversion between these two units again?". The problem isn't base 10 vs base 12, it's the fact that in SI, every unit scales in the same way (the prefixes). With imperial units, every unit scales differently. How many fl.oz to a tablespoon? No idea. How many teaspoons to a tablespoon? No idea.

Unless you are working with wold and the measurements are all nonlinear lies. https://en.m.wikipedia.org/wiki/Lumber#Dimensional_lumber

I've heard that and I don't disagree with it. But things fail really badly. E.g. 2 inches and 5 sixteenth

I find this hilarious when watching DIY videos on YouTube.

All the makers are talking about "5/16 of an inch" and I'm trying to convert this to a metric value and it doesn't make any sense at all, because "complex" fractions like this are not used in every day life.

Yep. Factoring is useful in a lot of cases.

Also, although not strictly a debate around metric, the Fahrenheit scale gives you more granularity without going to decimals and requires less use of negative numbers on a day to day basis. And, if one is really concerned about a scientifically relevant temperature scale, we'd be using Kelvin, not Celsius.

Kelvin IS Celsius, only starts at absolute zero. 0 C is 273 Kelvin, and 0 Kelvin is -273 Celsius. You add 273 to any Celsius measurement, and voila, it's Kelvin.

No. That's actually not quite correct. You add 273.15... The size of the degree is the same of course.

My point is that if you want to use a "correct" scientific measurement on a day to day basis you'd use Kelvin. As soon as you're converting, you're converting whether from Celsius or Fahrenheit.

ADDED: There's an argument for Celsius vs. Fahrenheit of course in so far as the size of the degree is baked into some other SI measurements. But there's no particular other reason that Celsius is superior on a day to day basis other than familiarity for some. There's some logic to basing easy to remember numerical points around water properties but it's not clear that actually has a lot of advantages for day-to-day questions about how hot or how cold it is.

The fact that degree is the same means that energetically 1 degree C is equal to 1K. So when doing scientific calculations, for example to calculate energy needed to change the temp by X, they are the same. The fact that the scale is based on water properties seem to be just so values are easier to relate to. We are water based, after all.

Can anyone provide any reason to use Fahrenheit scale, apart from historical ones? Legit question.

Sure. Where I live:

1. Fahrenheit is far more likely to cover the range of temperatures I encounter without having to use negative numbers. 0 is really cold. Anything below zero is really freaking cold. The temperature of the boiling point of water is mostly an academic point in my day to day life.

2. Fahrenheit provides about 2x the granularity of Celsius without having to use decimals

I'm not going to argue that if Fahrenheit didn't exist, we'd invent it. But it does have some advantages as an existing system.

ADDED: For engineering using SI units, of course Celsius and Kelvin make a lot more sense.