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 - 136: Supported
  4. ✅ 137: Supported
  5. ✅ 138 - 140: Supported

Edge

  1. ✅ 12 - 136: Supported
  2. ✅ 137: Supported

Safari

  1. ❌ 3.1 - 5.1: Not supported
  2. ✅ 6: Supported
  3. ✅ 6.1 - 18.4: Supported
  4. ✅ 18.5: Supported
  5. ✅ 26.0 - TP: Supported

Firefox

  1. ❌ 2 - 3.6: Not supported
  2. ✅ 4 - 15: Supported
  3. ✅ 16 - 138: Supported
  4. ✅ 139: Supported
  5. ✅ 140 - 142: Supported

Opera

  1. ❌ 9 - 12.1: Not supported
  2. ✅ 15 - 116: Supported
  3. ✅ 117: Supported

IE

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

Chrome for Android

  1. ✅ 137: Supported

Safari on iOS

  1. ❌ 3.2 - 5.1: Not supported
  2. ✅ 6: Supported
  3. ✅ 7 - 18.4: Supported
  4. ✅ 18.5: Supported
  5. ✅ 26.0: Supported

Samsung Internet

  1. ✅ 4 - 27: Supported
  2. ✅ 28: Supported

Opera Mini

  1. ❌ all: Not supported

Opera Mobile

  1. ❌ 10 - 12.1: Not supported
  2. ✅ 80: 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. ✅ 137: Supported

Firefox for Android

  1. ✅ 139: Supported

QQ Browser

  1. ✅ 14.9: Supported

Baidu Browser

  1. ✅ 13.52: 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