As an impulsive maker with bad handwriting and tendency to be a little fast and furious with my math on home projects, I’ve relied on calculators and unix tools to assist. While there’s lots of description as to what out there in the hand-held calculator world (which I won’t repeat here), there’s no so much on what accessible on the desktop or what goes beyond the handheld calculators. It’s not the easiest topic in the world to Google for, either (lots of hits due to generic search terms), so I’ve gathered a few that I thought were particularly interesting and useful (and free).
Units
I start with the old standby, the Unix units program. It’s installed as part of the standard distribution and has a very large list of built-in conversion factors. It’s output syntax is a little wonky, but not hard to get used to:
following:
You have: grains
You want: pounds
* 0.00014285714
/ 7000
Units is purely command-line based.
Uconeer
Katmar Software produces a interesting conversion tool for engineers called Uconeer. Uconeer has a GUI, and an intense list of 397 units in 46 categories. They are not kidding, however, that it is targeted for engineers. The list of factors are probably not ones that the average home maker is going to come across that often. Still, it looks impressive to leave that enthalpy conversion on your desktop.
Uconeer is download only, there is no online or web experience (other than the docs).
Online Web Conversions
Lawrencegoetz.com has a rather straightforward conversion program that is entirely web-based. This site understands only length, temperature, weight, and volume and enumerates your options at each step. It’s functional, but primitive if you’re staying in this realm.
Convert-me is a little heavy on the ads and blinky layout, but offers a web GUI-based way to convert in about 17 diverse categories. One unusual feature is that some screens have multiple output conversions. This could be handy if you want to see your results as expressed by many units simultaneously.
Frink
I’ve saved the best for last.
I’ve been having a lot of fun with Frink. It’s a calculating tool with a crazy large vocabulary of built-in knowledge about the universe. At its most straightforward, it is able to convert between these types, and invisibly keeps track of any conversion along the way. If you liked any of the above, you will be elated with Frink.
The manual is detailed, approachable, and written humorously. Example:
Movie Magic
In the movie Independence Day, the alien mother ship is said to be 500 km in diameter and have a mass 1/4 that of earth’s moon. If the mother ship were a sphere, what would its density be? (The volume of a sphere is 4/3 pi radius3)
1/4 moonmass / (4/3 pi (500/2 km)^3) -> water
280.68
This makes the ship 280 times denser than water. This is 36 times denser than iron and more than 12 times denser than any known element! As the ship is actually more a thin disc than a sphere, it would actually be even denser. Since it contains lots of empty space, parts of it would have to be much, much denser.
If the object is this dense and has such a large mass, what is its surface gravity? Surface gravity is given by G mass / radius2, where G is the gravitational constant (which Frink knows about):
G 1/4 moonmass / (500/2 km)^2 -> gravity
2.000079
The surface gravity of the spaceship is thus at least twice earth’s gravity–and that’s on the rim where gravity is weakest. It would actually be much higher since it’s much, much flatter than a sphere. I hope you’re not the alien that has to go outside and paint it.
I’m guessing that Frink will be a great Makers tool. With a few clicks seeing relationships between light/heat/weight/mass/time/dates are all accessible, with perfect transparency and accuracy in the conversion.
Here’s an example of the online applet wherein a some builders from Junkyard Wars to calculate how long it will take to pump air down a barrel that been submerged two fathoms below the water. If the guy can sustain 40 watts of pumping power, how many minutes will it take to fill the barrel?
Rather than muck around with weight/strength calculation for your new geodesic dome, or try to get the units right in figuring out how far your solar robot can go, you can get it right the first time with Frink.
I think it also will be a great educational tool. I’ve played around with a few examples to determine how long it would take to drive to the nearest star and how much an ant would weight if it were the size of a house.
The Frink doc is full of Sample Calculations, and there’s a ready to use, no install applet. There’s also an embeddable version (with Java), a downloadable Jar, and even mobile versions available. When allowed to connect to the internet it will even do certain types of financial and language conversions.
I’d read a bunch of the sample calculations and get a feel for it before jumping into the applet.
Congrats to Alan Eliasen for producing a cool tool such as this (and taking the time to document and sharing it properly)!