How do I buy iCloud Storage?

You can't buy extra iCloud storage with a one-time purchase, but you can pay monthly for more by subscribing to iCloud+.

On an iPhone:

1. Go to Settings, then tap your name. 
2. Tap iCloud, then tap Manage Account Storage or Manage Storage. Or scroll down and tap Upgrade to iCloud+.
3. Tap Buy More Storage or Change Storage Plan.
4. Choose a plan and follow the onscreen instructions.

On a Mac:

1. Choose Apple menu  > System Settings or System Preferences.
2. Click Apple ID.
3. Click iCloud.
4. Click Manage. Or scroll down and tap Upgrade to iCloud+.
5. Click Change Storage Plan or Buy More Storage, and choose a plan.
6. Click Next and enter your Apple ID password.

Upgrade to iCloud+ - Apple Support