Alegre Software has announced Plethora, a measurement unit conversions calculator for Mac OS X. It boasts hundreds of metric/S.I., imperial, U.S., and other units in its database, most to 14 significant digit precision.

New units can be added by the user. Plethora supports compound units such as pounds and ounces, ft/in/fractions, scientific notation and control of significant digits.

Plethora costs US$9.95 and can be downloaded at .