Can I use
?

calc() as CSS unit value

- CR

Method of allowing calculated values for length units, i.e. width: calc(100% - 3em)

Chrome

  1. 4 - 18: Not supported
  2. 19 - 25: Supported
  3. 26 - 118: Supported
  4. 119: Supported
  5. 120 - 122: Supported

Edge

  1. 12 - 118: Supported
  2. 119: Supported

Safari

  1. 3.1 - 5.1: Not supported
  2. 6: Supported
  3. 6.1 - 17.0: Supported
  4. 17.1: Supported
  5. 17.2 - TP: Supported

Firefox

  1. 2 - 3.6: Not supported
  2. 4 - 15: Supported
  3. 16 - 119: Supported
  4. 120: Supported
  5. 121 - 123: Supported

Opera

  1. 9 - 12.1: Not supported
  2. 15 - 103: Supported
  3. 104: Supported

IE

  1. 5.5 - 8: Not supported
  2. 9: Partial support
  3. 10: Partial support
  4. 11: Partial support

Chrome for Android

  1. 119: Supported

Safari on iOS

  1. 3.2 - 5.1: Not supported
  2. 6: Supported
  3. 7 - 17.0: Supported
  4. 17.1: Supported
  5. 17.2: Supported

Samsung Internet

  1. 4 - 22: Supported
  2. 23: Supported

Opera Mini

  1. all: Not supported

Opera Mobile

  1. 10 - 12.1: Not supported
  2. 73: Supported

UC Browser for Android

  1. 15.5: Supported

Android Browser

  1. 2.1 - 4.3: Not supported
  2. 4.4 - 4.4.4: Partial support
  3. 119: Supported

Firefox for Android

  1. 119: Supported

QQ Browser

  1. 13.1: Supported

Baidu Browser

  1. 13.18: Supported

KaiOS Browser

  1. 2.5: Supported
  2. 3: Supported

Support can be somewhat emulated in older versions of IE using the non-standard expression() syntax.

Due to the way browsers handle sub-pixel rounding differently, layouts using calc() expressions may have unexpected results.

Resources:
MDN Web Docs - calc
Mozilla Hacks article
WebPlatform Docs