Let's say a player has to make a saving throw or take 20 cold damage. If they succeed on the save, they take half damage (10).
Resistance also halves damage. What happens if they have cold resistance and succeed on said saving throw? Do they take half damage (10) or quarter damage (5)?
Best Answer
You take 1/4 the total damage. You are looking at two separate events. The first event is whether or not you are hit with the 'full force' of the attack (your saving throw determines this). You can think of it like diving out of the way of a fireball, or ducking under a column of ice.
If you pass the saving throw, you take half (you successfully avoided some of the damage). If you don't, you take the full amount.
Now, after this, you resolve your resistances. From the Basic Rules, p75:
(Emphasis mine)
At this point, you've already determined how much damage you were going to take due to your saving throw (either half or full). Now, you take the amount of damage you would have taken, and then take half of that because you have resistance to that damage type.