A mile is supposed to be (1 / 60 / 360 / Earth.circumferenceOf()), so a 1.5mi radius or 3mi diameter circle is (supposed to be slightly short of) 3/60 or 0.05 degrees on a map.

A yard is just 10% short of a meter, just the same thing for most practical purposes.

(full disclosure: I did look these up)

Metric rules and imperial drools, I agree, but I reckon if we put our minds to it we can multiply by 0.9 and 1.6 (or 0.91 and 1.61 if you are genius). Keeps the mind sharp in this age of outsourced thinking!