I’m pretty much a fan of unit conversion tools. Everywhere I read references to measurements of temperature, weight, speed. These are often given in imperial or US units, but I’m more familiar with the metric system. I often resort to Google for this, because they had this very clever idea of incorporating a unit conversion tool into their search engine. The problem was that I could only use this while online, and an offline alternative was an essential need.
Then it hit me. What if Alfred be able to do it? I’m a developer, and Alfred is extensible, so I got onto a new project to develop an Alfred extension to do this, just like Google does. Today I think my project is stable enough so I decided to go public with it. You can download the extension here.
How to use it
I’m assuming you’re already an Alfred user with the Powerpack installed. You’ll also be needing Growl to be able to see the results of your queries. After downloading and installing this extension, you can trigger unit conversions with the keyword cv (as in convert). You can change that to something else of your preference, of course.
Performing a unit conversion query with Alfred
Using it is simple. You open the Alfred command window, type the extension keyword and the query and press ENTER. You’ll see the results shown in a Growl notification, and you’ll also get the results copied to the clipboard.
As for the queries and how to phrase them, I won’t make an exhaustive explanation here. I rather prefer to list here some examples of valid unit conversion queries that you can perform. This will give you an idea of how to phrase queries and a sample of the variety of units supported out-of-the-box. The following are examples of valid queries. Be sure to type them in Alfred preceded with the keyword for the extension.
- 10 km in miles
- 100 kph in miles per hour
- 50 pounds in kg
- 134.5 seconds in minutes
- 200 milliliters in cubic centimeters
- 2 acre foot per year in liters per day
- 3 newtons in lb ft / square second
- -40 fahrenheit in celcius
- 1 megaparsec in astronomical units
- 6.5e17 decays per minute in megabecquerels
- 10 gallons in liters
Note how you can refer to units by their long or short name, and also how unit prefixes (like kilo-, milli-, etc.) are supported too. Long unit names can be given in plural or singular form.
You can also convert sums of quantities…
- 1.5 weeks + 2 days in hours
- 2 miles, 3 furlongs and 25 yards in km
- 100 km/h, 10 m/s and 2 feet per minute in miles per hour
- 3 hours 15 minutes in seconds
…or omit certain parts of the query. The following are valid queries too. Try them to see the results.
- 3 leagues
- ounces in grams
- parsec
- 3 minutes 23 seconds
The math is performed internally without loss of precision, so you get very accurate results. Also, you can work with really large or small numbers. Try the following queries:
- 1 cubic parsec in cubic picometers
- 1e-50 meV in petajoules
Supported units and measurements
From the examples above you can get an idea of the range of units and physical properties it supports. I won’t list all the units here, but just to give an idea, this extension supports units over a wide variety of physical properties, most of which are listed below.
- Most common properties
- Length (distance), time, temperature, mass (weight), area, volume, density, speed, acceleration, angular velocity, momentum, force, pressure, work (energy), power, plane angle, solid angle, amount of substance.
- Electricity and magnetism
- Electric current, electric charge, voltage, resistance/conductance, capacitance, magnetic flux, inductance.
- Light and radiation
- Luminous intensity, luminous flux, illuminance, luminous energy (quantity of light), radiation dose, ionizing radiation, radioactivity.
- Other properties
- Catalytic activity, reciprocal length, acoustic impedance and resistance, thermal resistance, dynamic viscosity, molar concentration, mass flow, volumetric flow.
In addition to physical phenomena, this extension also supports conversion of currency and units of digital information, such as data size and data rate (e.g. bits, bytes, kilobytes, kbits per second). In this last case, in addition to the SI prefixes, it also supports binary prefixes like kibi-, mebi-, etc.
A note about currency exchange rates
In the case of currency conversion, the extension will attempt to update currency exchange rates from the Internet at most once every hour, but it keeps a local cached version. The extension can only update the cached version when it’s used, even if it is not used for currency conversion. But if you spend many hours or days without triggering the extension while being online, you’ll end up with outdated currency conversions.
Also note that currency exchange rates given by this application are for information purposes only. It will always be approximate to what you’ll actually get when exchanging money. For your information, currency exchange rates are obtained by the extension from a wonderful public API hosted at openexchangerates.org, which is based on the currency bot project.
What’s next
First of all, enjoy it. You can also contact me to send feedback, bug reports and suggestions of improvements and new features.
If you’re a developer, you can also contribute to the unit conversion engine that powers this extension. It’s an open source Java library that I authored and published on github. You can check it out here.
Simply click on it to be given the option to open it on Youtube instead.