If you convert from a different aspect ratio (like 16:9) it depends on the game and what you want to achieve.
When you convert between different aspect ratios you have to choose if you want to conserve the sensitivity vertically or horizontally, the 360 distance or the tracking distance.
A lot of factor play in here, including the game's FOV type, how it scales to aspect ratio and resolution. However you don't have to worry about any of this as long as you enter the correct values into the calculator. It will take all of this into account and give you the correct sensitivity based on your settings.