AppBreakup
Submit an app

Proton Calendar alternatives: 5 apps ranked by verified data

Facts checked Oct 25, 2026AppBreakup editorialHow we rank

Common reasons people leave Proton Calendar: no direct CalDAV sync with third-party clients, and fewer integrations than Google Calendar. We ranked 5 alternatives by how directly each one replaces Proton Calendar, then by reviews, real visits and how recently each app's facts were checked against its own website. Tuta Calendar currently ranks first.

Quick comparison

#AppPricingOpen sourcePlatformsVerified factsScore
1Tuta Calendar logoTuta CalendarFree plan + paidYesWeb, iOS, Android +34 of 466.5
2KOrganizer logoKOrganizerOpen sourceYesLinux4 of 455.3
  1. Tuta Calendar logo

    1. Tuta CalendarTop pick

    Best for: Privacy-focused users who want an encrypted calendar with open-source apps

    Free plan + paidOpen sourceWeb, iOS, Android, Windows, macOS, Linux

    66.5

    score / 100

    Why switch from Proton Calendar

    Another encrypted calendar with open-source apps and a free tier, based in Germany.

    Pros

    • Encrypted calendar with open-source clients
    • Apps on every major platform, including Linux
    • Android APK available outside Google Play

    Cons

    • Free plan limited to one calendar
    • No CalDAV sync with other calendar apps
    • Basic features compared with mainstream calendars
    Visit Tuta Calendar Details and reviews
    How this score is calculated
    Editorial fit ×0.3100
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.1585
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is Tuta Calendar a good Proton Calendar alternative?

    Verified facts

    4 of 4 verified
    Mobile apps
    Free, Android and iPhone
    Checked Oct 25, 2026tuta.com(opens source in a new tab)
    Desktop clients
    Open source for Windows, macOS, Linux
    Checked Oct 25, 2026tuta.com(opens source in a new tab)
    Free plan calendars
    1
    Checked Oct 25, 2026tuta.com(opens source in a new tab)
    Android APK
    Available from GitHub
    Checked Oct 25, 2026tuta.com(opens source in a new tab)
  2. KOrganizer logo

    2. KOrganizer

    Best for: KDE Plasma users who want a configurable desktop calendar with tasks and journals

    Open sourceLinux

    55.3

    score / 100

    Why switch from Proton Calendar

    Open-source desktop calendar you can point at your own CalDAV server.

    Pros

    • Events, to-dos and journal in one app
    • Integrates with KMail and the Kontact suite
    • Supports CalDAV, Google and groupware servers

    Cons

    • Dense, old-fashioned interface
    • Akonadi backend can be heavy to run and configure
    • Pulls in many KDE dependencies on other desktops
    Visit KOrganizer Details and reviews
    How this score is calculated
    Editorial fit ×0.363
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.1585
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is KOrganizer a good Proton Calendar alternative?

    Verified facts

    4 of 4 verified
    License
    GPL-2.0+
    Checked Oct 25, 2026apps.kde.org(opens source in a new tab)
    Part of
    Kontact suite
    Checked Oct 25, 2026apps.kde.org(opens source in a new tab)
    Features
    Events, tasks, alarms, web export
    Checked Oct 25, 2026apps.kde.org(opens source in a new tab)
    Platform
    Linux
    Checked Oct 25, 2026apps.kde.org(opens source in a new tab)

The best Proton Calendar alternative for…

The highest-ranked app in this list for each need.

Tuta Calendar logo

Best Proton Calendar alternative for most people

Tuta Calendar

Another encrypted calendar with open-source apps and a free tier, based in Germany.

Fossify Calendar logo

Best Proton Calendar alternative for a free option

Fossify Calendar

Local-only open-source Android calendar with no internet access.

Google Calendar logo

Best Proton Calendar alternative for a free plan you can upgrade

Google Calendar

Far more integrations and sharing, if encryption isn't a priority.

KOrganizer logo

Best Proton Calendar alternative for open source

KOrganizer

Open-source desktop calendar you can point at your own CalDAV server.

Tuta Calendar logo

Best Proton Calendar alternative for Mac

Tuta Calendar

Another encrypted calendar with open-source apps and a free tier, based in Germany.

Tuta Calendar logo

Best Proton Calendar alternative for Windows

Tuta Calendar

Another encrypted calendar with open-source apps and a free tier, based in Germany.

Tuta Calendar logo

Best Proton Calendar alternative for Linux

Tuta Calendar

Another encrypted calendar with open-source apps and a free tier, based in Germany.

Zoho Calendar logo

Best Proton Calendar alternative for iPhone and Android

Zoho Calendar

Free hosted calendar with business features, without Google.

Tuta Calendar logo

Best Proton Calendar alternative for working in the browser

Tuta Calendar

Another encrypted calendar with open-source apps and a free tier, based in Germany.

Proton Calendar alternatives: common questions

What is the best alternative to Proton Calendar?

Tuta Calendar ranks first right now. Another encrypted calendar with open-source apps and a free tier, based in Germany. Google Calendar and Fossify Calendar follow it in our ranking.

Is there a free alternative to Proton Calendar?

Yes. Tuta Calendar (free plan + paid), Google Calendar (free plan + paid), Fossify Calendar (open source) and Zoho Calendar (free) have a free option. Check each app's verified facts for current plan limits.

Is there an open-source alternative to Proton Calendar?

Yes: Tuta Calendar, Fossify Calendar and KOrganizer.

Which Proton Calendar alternatives work on Linux?

Tuta Calendar and KOrganizer run on Linux.

Why do people switch from Proton Calendar?

The complaints we hear most: no direct CalDAV sync with third-party clients; fewer integrations than Google Calendar; best value only if you use other Proton apps.

How is this list ranked?

Every app is scored with the same published formula: how directly it replaces Proton Calendar, reviews (weighted by verification), visits from AppBreakup, how recently its facts were checked against its own website, and reader votes.