A OneCal alternative for Google and Outlook calendars
OneCal and Caltsu both keep several calendars aware of each other. OneCal also covers iCloud and includes scheduling links and an AI assistant. Caltsu only syncs, copies nothing but the time, and has one €5 plan with no limit on calendars.
- Main job
- CaltsuCalendar syncOneCalCalendar sync, with scheduling links and an AI assistant on every plan
- What the other calendar receives
- CaltsuA block with the start and end time, the title Busy or your own text, and a note naming the source calendar. Never the event title, attendees, location, notes or meeting link.OneCalConfigurable. You can leave out event titles or choose which details to show.
- Google Calendar
- CaltsuYesOneCalYes
- Microsoft 365 and Outlook
- CaltsuYesOneCalYes
- Apple iCloud
- CaltsuNot yetOneCalYes. OneCal says iCloud changes take up to 10 minutes to reach other calendars.
- Connected calendars
- CaltsuNo limitOneCal2 on Starter, 5 on Essential, 50 on Premium
- Price
- Caltsu€5 per month or €48 per year. One plan, 14-day trial without a card.OneCalStarter $5, Essential $10, Premium $25 per user per month, or $60, $120 and $300 a year. 14-day trial without a card.
- Where the servers are
- CaltsuPostgreSQL in Frankfurt, GermanyOneCalIn the US, according to OneCal's privacy policy
| Topic | Caltsu | OneCal |
|---|---|---|
| Main job | Calendar sync | Calendar sync, with scheduling links and an AI assistant on every plan |
| What the other calendar receives | A block with the start and end time, the title Busy or your own text, and a note naming the source calendar. Never the event title, attendees, location, notes or meeting link. | Configurable. You can leave out event titles or choose which details to show. |
| Google Calendar | Yes | Yes |
| Microsoft 365 and Outlook | Yes | Yes |
| Apple iCloud | Not yet | Yes. OneCal says iCloud changes take up to 10 minutes to reach other calendars. |
| Connected calendars | No limit | 2 on Starter, 5 on Essential, 50 on Premium |
| Price | €5 per month or €48 per year. One plan, 14-day trial without a card. | Starter $5, Essential $10, Premium $25 per user per month, or $60, $120 and $300 a year. 14-day trial without a card. |
| Where the servers are | PostgreSQL in Frankfurt, Germany | In the US, according to OneCal's privacy policy |
OneCal details come from its public website, checked September 2026. Plans change, so confirm on their site before you decide.
When OneCal fits better
- You need iCloud calendars in the sync today.
- Some calendars should receive event titles, and you want to set that per sync.
- You want scheduling links and an AI assistant from the same vendor.
When Caltsu fits better
- Client or employer calendars must never receive a title, attendee or location, with no setting that could change that.
- Your IT team wants the database in the EU and a short list of OAuth permissions to review.
- You connect three or more calendars. OneCal's Starter plan covers two, so that means Essential at $10 or Premium at $25. Caltsu stays at €5.
What a client calendar sees from Caltsu
Every copied event becomes a block with its start and end time. The title defaults to Busy and you can change the text. The block description says which of your calendars it came from, such as "Blocked time from work@example.com". There is no setting that copies the event title, attendees, location, notes or meeting link, so nobody can switch it on by mistake.
Permissions and data handlingClient calendar, Tuesday
Steering group09:00-10:00
Busy10:30-11:15
Busy13:00-14:30
Sprint review15:00-16:00
Common questions
- Is Caltsu cheaper than OneCal?
- It depends on how many calendars you connect. OneCal Starter is $5 per user per month for 2 connected calendars, Essential is $10 for 5 and Premium is $25 for 50. Caltsu is €5 a month or €48 a year for any number of Google and Microsoft calendars.
- Does Caltsu sync iCloud calendars like OneCal?
- Not yet. Caltsu syncs Google Calendar, Google Workspace, Microsoft 365 and Outlook.com. If you need iCloud in the sync today, OneCal supports it.
- Where do Caltsu and OneCal keep their data?
- Caltsu's database runs in Frankfurt, Germany. OneCal's privacy policy, dated 18 August 2026, says its servers are in the US and that it relies on Standard Contractual Clauses for data from the EU.
- How do I switch from OneCal to Caltsu?
- Start a Caltsu trial, connect the same Google and Microsoft accounts and put the calendars in one sync group. Then turn off the syncs in OneCal. If copies of events made by OneCal are left in any calendar, delete them so the same time is not blocked twice.
- Do both have a free trial?
- Yes. Both offer 14 days without a credit card. Neither has a free plan after the trial.
Try it on your own calendars.
Other comparisons: CalendarBridge, Reclaim.ai, Clockwise, Cal.com