In the game you find the setting under Settings → Mouse & Keyboard → Aiming → Mouse Sensitivity.
Applies to Modern Warfare (2019 and later), Warzone and Black Ops 6. Menu names can differ between titles.
Conversion
Apex Legends to Call of Duty Sensitivity
In short: Apex Legends sens times 3.3333. 1.2 becomes 4. For your own value, just edit the sentence below.
How to set it in Call of Duty
What changes when you go from Apex Legends to Call of Duty
Apex Legends turns 3.33 times further per mouse count than Call of Duty. That is why the number gets bigger while your mouse distance stays the same.
Call of Duty shows 25.5° less field of view than Apex Legends by default (80° against 105.5°). The picture looks a little tighter and movement on screen a little faster. For Apex Legends the field of view is only a rough guide, check it in the game.
In Call of Duty you can enter up to 2 decimal places. Use all of them to keep the conversion exact.
Common questions
How do I convert Apex Legends sens to Call of Duty?
Multiply your Apex Legends sens by 3.3333. 1.2 in Apex Legends becomes 4 in Call of Duty.
Where do I set the sens in Call of Duty?
Settings → Mouse & Keyboard → Aiming → Mouse Sensitivity. Applies to Modern Warfare (2019 and later), Warzone and Black Ops 6. Menu names can differ between titles.
Why does Call of Duty still feel a bit different?
Apex Legends: Slider from 70 to 110 (about 105 to 106° horizontal at 90). Call of Duty: Slider from 60 to 120 (horizontal, default 80). Match the field of view as closely as you can; then the converted sens feels most natural.
Does this also apply to scopes?
No. The values are for hipfire. Zoom and scope sensitivities are set separately in the game.
Should I change my DPI?
No. Keep your DPI and only change the sens in the game. That keeps your feel the same everywhere.