Numi is calculator that allows to describe tasks the natural way and instantly get an accurate answer. For example, $20 in euro - 5% discount or today + 2 weeks.
To use workflow make sure Numi installed and running. Prefix your calculations with 'n': 'n (20% of 45)/12', 'n $20 in Euro' or 'n time in Tokyo'. Testing Alfred support ATM, so, it only available in development version (download at http://numi.io/static/dev/Numi.zip)
Numi workflow: http://www.packal.org/workflow/numi
Will appreciate for feedback!