Do you expect all memes and jokes to be absolutely harmless and 100% politically correct for every nation/culture/race/gender/<group>?
50F -> 10C
51F -> ~10.5C
52F -> ~11C
Unless you hate decimals, I don't think there's much granularity gained. X = 33% --> 33% * 33.5M / 52M = 21.5%
X = 50% --> 50% * 33.5M / 52M = 32.2%
X = 75% --> 75% * 33.5M / 52M = 48.3%
Your estimations would hold iff >75% of the land in the circle is habitable.