Proton Calendar review

Proton Calendar is for people who see their calendar as private data. Proton says it secures all events with end-to-end encryption, and that event details including the title, description, location and people invited are encrypted so not even Proton can see them; events from people on other calendars are protected with zero-knowledge encryption. The free plan includes 3 personal calendars and lets you send and receive invitations. Upgrading to Mail Plus raises the limit to 25 calendars and adds calendar sharing; it was $2.49 a month for the first 12 months on yearly billing when we checked, renewing at $47.88 a year. Proton is based in Switzerland. The tradeoff for this list's purpose is that Proton Calendar is built to keep your schedule inside Proton, not to merge a Google work calendar and an Outlook account into a single view, so it suits people moving their personal schedule into a private home.

Who it is for

privacy-minded people who want their events encrypted

Price

Free plan with 3 personal calendars; Mail Plus with 25 calendars $2.49 per month billed yearly for the first 12 months, then $47.88 a year.

50% off Mail Plus $4.99 $2.49 /month
Quoted from the vendor pricing page on November 12, 2026.

Key features

• End-to-end encryption for event titles, descriptions, locations and invitees
• Free plan includes 3 personal calendars; paid plans include 25
• Calendar sharing on paid plans
• Send and receive invitations on every plan
• Bundled with Proton Mail and other Proton apps

Strengths and weaknesses

• Strength: Proton says even it cannot see event details
• Strength: Free plan available
• Strength: Swiss company under Swiss privacy law
• Weakness: Calendar sharing is not included on the free plan
• Weakness: Free plan limited to 3 personal calendars
• Weakness: Not designed to merge Google or Outlook accounts into one view the way Notion Calendar or Fantastical do

Key facts

• Free plan: 3 personal calendars
• Paid calendars: 25 personal calendars
• Mail Plus: $2.49 per month for 12 months billed yearly, renews at $47.88 a year
• Encryption: End-to-end for event details

Where it ranks

Proton Calendar is No. 9 in our Best Calendar Apps verdict.