If you spend a lot of time on sewing blogs and love US patterns such as those from Colette, Oliver + S and Amy Butler, you probably work in inches much of the time. That's cool, my tape measure can deal with that. But uh oh, what if you want to order fabric from a UK site or shop and need to know your requirement in centimetres? Ugh. It's a daily irritation.
The Convert Units iPhone app has been indispensable. Love.