Halfway to Metric
I have an idea that will help transition America to the metric system.
(I think meters are actually pretty reasonable, though.. you’ll see)
We transition to a metric system, one based on the foot. Out with the meter, in with the foot.
Call it American metric.
It’s the 40 yard dash, the ten foot pole, the feet that fit size 14 shoes. In retrospect, that last one is a bit absurd. And that first one is technically yards, but when I say yard your head says 3 feet.
When I ask how tall is Mt Everest you’ll say something crazy like 29 thousand feet, when maybe a mile (or a furlong, or a kilometer..) would be a more useful measure at that scale. Our own daytoday speech, if you look at it, wins out hugely in favor of the foot.
The basic conversions are:
SI metric  foot metric 

25.4 mm  1/12 foot (an inch) 
.3048 m  1 foot 
304.8 m  1 kilofoot 
1 Km  3.28 kilofeet 
So, roughly:
Distance
footmetric  approximately 

7.2 nanofeet  diameter of a DNA helix 
200 microfeet  thickness of a human hair 
3 millifeet  thickness of a credit card 
1 foot  .. everyone knows this, that’s the point 
1 kilofoot  3 football fields 
100 kilofeet  25 minute car trip 
1 megafoot  3 hour drive, as tall as Pennsylvania 
100 megafeet  circumference of Earth 
1 gigafoot  distance from Earth to the Moon 
24 terafeet  distance from Earth to Pluto 
807 exafeet  distance to Sagittarius A**, near center of Milky Way 
79 zettafeet  distance to Andromeda Galaxy, a very nearby galaxy 
993 yottafeet  distance to GNz11, a most farout galaxy 
The Orders of Magnitude on Wikipedia is a great resource.
Speed
I think anything per hour, unless we can all go base60, is hard to think about the 3600 factor between seconds and hours. So transitioning to anythingpersecond is a great move (IMHO), and milespersecond is just inconceivable.
feetpersecond » milesperhour
footmetric speed  approximately 

1 foot / second  .68 mph 
100 feet / second  68 mph 
100 feet / second  110 km/h 
1 kilofoot / second  speed of sound 
4 kilofeet / second  a bullet, leaving a rifle 
56 kilofeet / second  Voyager I, from the Sun 
1 gigafoot / second  speed of light 
1 foot / second is just over 1 kilometer / hour
So those little yellow numbers on your car dashboard are a decent reference point: if you’re going 60mph, you can see you’re at 96.6km/h, which is 88f/s. ^{1}
Plus, you know how the speed of light is either 3e8 or some weird 186something number? It’s actually really reasonable as 983,569,089.2.., which is just 2% off an even c = 1 gigafoot / second.
To be exact, the speed of sound is ~1.125 kilofeet / second, so 1 kf/s is 12% low. But, rejoice in the fact that as altitude rises & temperature drops, the speed will decrease towards 1 kf/s, which is accurate around 40F / 40C.
Area
size  thing of approximate area 

1 sq ft  you know this, Chief 
100 sq ft  a small room 
10,000 sq ft  a decentsized front & back yard, ¼ acre 
1 sq kft  56 Walmart Supercenters 
100 sq kft  3 Central Parks 
10,000 sq kft  Prince William County 
1 sq mft  3 Hawai’is (the big island, three of ‘em) 
Why?
I think it’s nice to scale things in terms of 10s (1, 10, 100..), but also in √10s: 1, 3, 10, 30, 100, 300.. etc.
10 feet is between 1 m and 10 m. 100 megafeet is between 10 Mm and 100 Mm. Basically:
5 ft, 5 m, 50 ft, 50 m, 500 ft, 500 m..
We don’t have to transition away from feet to gain metric: we can have both feet & meters. ¿Por que no los dos?
I wish we all just used metric, but as long as we’re seemingly not going to drop a footbased system, we might as well make it our own footmetric.
Taking it to perfection
I think the meter is pretty arbitrary anyways, so they should just readjust the meter (or the yard) to match √10 feet. Just for fun, we could call it a leg, but I’ll call it a meter:
1 m = √10 ft = 37.947.. in
That way, 1 m = 3.16227 ft, and 3.16227 m = 10 ft, so on & so on. I don’t think the rest of the world will oblige, though. We actually adjusted our foot to be 0.3048 m back in 1959, so maybe they could return the favor, and be a little irrational and set the meter back to 1 m = √10 0.3048 oldmeter = 0.964.. oldmeters. We adjusted our unit by 2 partspermillion, and they’d have to change by 3.6%, but hey it’d be a great signal of their, uh, willingness to advance mankind.
And maybe later, we can switch to base12.

It would’ve been really cool for the DeLorean in Back to the Future to have to hit 88 feet / second, which is certainly more realistic than the 88mph they portray, given the engines those things actually had. 88 feet / second is exactly equivalent to 60 miles / hour. Exactly. Yeah. Oh well. ↩