The NB calculator asks for current temp, the tasty brew calc asks for fermentation temp. Which do you use? The amounts come out dramatically different.

You should use the highest temperature the beer was at since the end of fermentation.

As the beer sits, the dissolved CO2 left over from fermentation comes out of solution and escapes out the airlock, until it reaches an equilibrium. The remaining amount of CO2 in the beer at the equilibrium depends on what the temperature is, so the calculators take this into account when they show how much additional sugar you will need to generate a desired level of CO2 saturation.