Fallout 4 is a single-player RPG where aiming is rarely time-critical, helped along by VATS. A comfortable medium around 25cm to 40cm per 360 is plenty.
As the sole survivor of Vault 111, you enter a world destroyed by nuclear war. Every second is a fight for survival, and every choice is yours. Only you can rebuild and determine the fate of the Wasteland.
Fallout 4 is a single-player RPG where aiming is rarely time-critical, helped along by VATS. A comfortable medium around 25cm to 40cm per 360 is plenty.
Use the calculator above. Enter the game you currently play, your in-game sensitivity and your DPI, then choose Fallout 4. It keeps your cm/360 the same, so the converted sensitivity feels identical to what you already aim with.
Most players use 400 or 800 DPI and set their in-game sensitivity from there. The DPI itself matters less than your cm/360, the distance you move the mouse for a full turn. Pick 800, set your Fallout 4 sensitivity to land in the range above, and leave it alone.