insulin carb ratio, UK and US

[jakaplan]

I recently purchased an insulin dose calculator that, I believe, comes from the UK. The directions say to input your insulin/carb ratio and they give examples of : 0; 1.0; 1.5; 2.0; 2.5; 3.0; 3.5. That is not what I am use to seeing here in the US for insulin carb ratios. A more typical ratio here would be 1:10 or 1:15. Can anyone explain how the British format translates to the US format or give me an explanation for what the numbers mean (1.0 or 2.5 for example) in the British format?
Thanks

 

[AMBrennan]

Educated guess: It's the number of units needed for one Carbohydrate Portion (CP) (=10g carbs). So 2.5 means 2.5u per 10g carbs, or 1:4 whilst 1.0 means 1.0u per 10g carbs, or 1:10