Imperial is easy to eyeball and is in human sized chunks of understanding. Metric is precise and easy to do math with.

Imperial measurements were based on physical objects that were commonly available to people at the time. Which made measuring imprecise but practical for people.

Metric was developed to use as few physical objects as possible to precisely define any unit of measure. These days they are defined by fundamental aspects of the universe so anyone can come up with the same measurements.

Imperial as it stands today is now defined by metric measurements because we need to be precise.

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The metric system was designed to, as much as possible, use scientifically measurable things for its units and that the "bigger versions" of units are just multiples or fractions of 10, 100, 1000, etc.

Most of the measurements involve water. A litre of water on earth at sea level (average conditions, admittedly) weighs exactly 1 kilogram and in a square shape would be exactly a box 10cm by 10cm by 10cm. Similarly a square of water 1m on each side is 1000 kg, or a ton. So now you have a way, given only the definition of a meter, to get the weight of a kilogram or vice versa.

Whereas the imperial system has a "foot" defined by... I'm not sure what really, but it divides into 12 inches, or can be combined by 3 to make yards, or 5280 to make miles. Eww, what terrible numbers. In metric a kilometer is just 1000 meters. A kilogram is 1000 grams. Etc. Nice consistent numbers.

Both are systems of measurement. In the metric system, to convert a bigger unit to the next smallest unit, you divide by 10. To covert a smaller unit to the next bigger unit, you multiply by ten. This makes it very easy to use and accounts for its popularity.

The metric system originated in France after the French Revolution, and today has been adopted worldwide as an international standard. Even the few countries that still use the imperial system have adopted the metric system for most industrial and scientific purposes.

The imperial system originated in England, and spread throughout the countries in the British Empire, many of which now belong to the British Commonwealth. It's not the same system used in the United States, although it's similar. That's because the imperial system was not standardized until an Act of Parliament in 1824. So there are some differences between the American system and the imperial system.

The imperial system contains a lot of historical quirks that make it harder to use than the metric system. But it has been used for so long that it survives in many places.

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One point of defense for the imperial system I'll add, is that it's easier for uneducated people to do math with.

A lot of the imperial system revolves around counts of 12 and 16, it's dumb and overly complicated for a number of reasons but it makes sense for dumb math.

Let's say I'm measuring 2 feet, or 24 inches.

I can easily divide up 24 by 2, 3, 4, 6, 8, 10, 12, etc.

If I have 20 CM and want to divide that up easily, I pretty much only have 2, 4, 5, and 10.

I'm not defending the Imperial system and Metric is better in so many ways. But this might help you realize how and why the imperial system was developed to be what it is, and why it was so useful for so long.

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> Imperial is easy to eyeball and is in human sized chunks of understanding. Metric is precise and easy to do math with.

This is just what Americans think because they use imperial units for everyday stuff and metric for science. In countries that use metric for everything, people find metric units "easy to eyeball" and are confused by imperial units. In the UK we use a mixture of both to some extent. For some quantities (e.g. people's weights) I'm much more familiar with imperial units and they seem "easier to eyeball", for others (e.g. temperatures) I'm the opposite, and for others (e.g. short distances) I'm pretty much equally comfortable with both.

Anyway, an important part of the design of metric units is that they try to minimize the use of conversion factors. For example, take the equation "power = force x velocity". In SI, the standard unit for force is the newton, the standard unit for velocity is the metre per second, and if you multiply a force in newtons by a velocity in metres per second, you get the power in watts, which is the standard unit. To do the equivalent in imperial units, you multiply the force in "pounds force" by the velocity in feet per second, and then you have to multiply by the conversion factor of 550 to get the force in horsepower. You inevitably need some conversion factors in some places, but metric units are designed so that you generally don't need them in the most common kinds of calculations, while in imperial units they're virtually everywhere. This is the main thing that makes imperial units inconvenient for scientific purposes (along with the fact that there are often multiple competing definitions of the same unit, leading to frequent confusion). As a general rule, they are just as "precise" as metric units.

12 inches in a foot

3 feet in a yard

1760 yards in a mile

I don't see how this is multiples of 12 honestly.

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