I see a lot of American sewers struggle with buying and using European and Australian patterns and fabrics/supplies, which are typically drafted and measured in centimeters rather than inches. There’s no need to buy a metric/Imperial ruler or retake your measurements in centimeters though; you can just do the conversion in Google’s search box. I use this tool all the time.
If I am buying a bra kit from Dutch Merckwaerdigh and want to know what the width of a 14 centimeter wide lace is in inches, I go to google.com and type 14cm to in. Turns out 14 centimeters is about 5 1/2″. Google automatically converts it for me, and even provides a calculator for further conversions.
The right and left side of the calculator are independent of each other, so if you wanted to convert 10 inches to centimeters you could just fill in the Inch textbox on the right, and it will do the conversion.
Even though I am American I like taking my measurements in centimeters, especially for very closely fitted things like bras, because the leap from centimeter to centimeter is smaller than from inch to inch. It feels more accurate. I also convert the metric charts provided by the pattern designer to inches myself because some companies round up/down more than others.
You can also use Google to convert currency to the current exchange rate too.
If I am buying a $14 paper pattern from Australian Style Arc and want to know how much that is in US dollars, I go to Google and type 14 aud to usd.
Likewise if I am purchasing two meters of stretch bengaline from Nortex Mill and want to know how much it will cost in British pounds I type 14.1 gbp to usd.
And if I am buying a €15 pattern from Italian Marfy I type 15 euros to usd.
For a $9.98 Canadian Sewaholic pattern I type 9.98 cad to usd.
The one catch is that if you are paying with Paypal they add on a fee, so the total amount will be a little more than what the currency converter shows. Think of it as a ballpark estimate rather than exact amount.
You can also convert temperature. I bought some wool crepe from a British seller and the care instructions mentioned hand washing in 30°C water. I typed 30 celsius to f in Google and found out that’s 86°F.
You can also convert things like mass (kilos to pounds) or measurements (ounces to teaspoons).