Guides · Updated 2026-10-29

How do I stop double bookings with several calendars?

Why do I still get double-booked after connecting my calendars?

A booking tool blocks a time slot only when two things are true: the event sits on a calendar the tool has been told to check, and the event’s status counts as busy. Connecting an account is not enough. Calendly’s Google Calendar guide says to “Choose the calendars you want Calendly to check for availability” and that “You’ll be marked as unavailable during any busy events on those calendars” (Calendly help).

In a Calendly Community thread about bookings landing on top of meetings from a second Google account, the poster had connected both accounts but had not ticked the second account’s calendar under “check for conflicts”. Calendly staff also pointed out that events named “busy” were not actually set to Busy (Calendly Community). A thread titled “My google calendar is synced, but my calendly availability isn’t changing” has over 10,000 views (Calendly Community).

Check first: open the booking tool’s calendar settings, list every calendar that holds real commitments (work, personal, family, team), and make sure each one is connected and ticked for conflict checking.

Which calendars does a booking tool check for conflicts?

Each tool checks only the calendars you select, and each has its own limits:

How many calendars can a free plan check?

Free plans often limit calendar connections, which is a common reason a personal calendar never blocks work bookings. Calendly’s pricing page lists “One calendar connection” on its Free plan and 6 calendar connections on paid plans in its comparison table (Calendly pricing). Zoho Bookings syncs one calendar on Free, two on Basic and up to six on Premium (Zoho). Google appointment schedules check secondary calendars only on an eligible paid plan.

12 of the 16 scheduling tools we rank have a free plan. Chili Piper, Acuity Scheduling, SavvyCal and Microsoft Bookings have no free plan.

From each vendor's pricing page; see free scheduling tools for what each free plan includes and leaves out.

If your free plan checks only one calendar, a workaround is to share your other calendars into the one account the tool reads, then select them there. This works only if the tool can read shared calendars from that account (see below).

Sub-calendars can count against more than one limit. Calendly staff explain that sub-calendars under one Outlook connection count as a single connection, but Calendly can check only up to four of them, a limit they attribute to Microsoft (Calendly Community).

Why don’t all-day events or “Free” events block my booking page?

Booking tools skip events marked Free. Calendly says all-day events “If set to ‘Busy,’ they can block your whole day”, and suggests marking holidays as Free so they don’t (Calendly help). Google says “No appointment times show up on days where you have an all-day event set to ‘Busy’” (Google help). Doodle lists events “marked as ‘free’ and not ‘busy’” as the likely reason times still look open (Doodle help).

Fix: open the event and set Show as (Google: Busy/Free; Outlook: Busy, Tentative, Away) to Busy for anything that should block bookings, including all-day trips or days off.

Do tentative events block bookings?

Tools treat tentative events differently:

• Calendly with Outlook: by default Calendly marks you unavailable for Outlook events labelled Busy, Tentative, Away / Out of Office and Working Elsewhere, and you can change which statuses count (Calendly help). In an Exchange calendar, “Working elsewhere” is read as available (Calendly help).
• Google appointment schedules: answering “Yes” or “Maybe” to an invitation removes that time from your booking page (Google help).
• Microsoft Bookings: a staff member’s busy time shows “as busy or tentative” and blocks that slot when the free/busy setting is on (Microsoft Learn).

Why aren’t shared, subscribed or delegate calendars checked?

Calendars you don’t own are the hardest case:

• Subscribed (ICS) calendars: Calendly staff say “Calendly is not able to check subscribed calendars for conflicts”, and suggest copying those events onto your own calendar as Busy (Calendly Community). Outlook itself refreshes subscribed calendars only about every 3 hours for personal accounts and every 6 hours for work accounts (Microsoft support).
• Shared mailbox or delegate calendars in Microsoft 365: Calendly reads them only after you add the shared calendar to your own account; “Open another mailbox” alone is not enough, and you need “Delegate (Can Edit) permissions” to add bookings to it (Calendly help).
• Google shared calendars: Calendly staff say calendars shared with only free/busy access can be checked for conflicts but not written to (Calendly Community). Google warns that a schedule created on a shared calendar “may not be possible to select other calendars to be reviewed for conflicts” (Google help).
• Co-hosts on Google appointment schedules: “By default, appointment schedules do not check co-host availability” (Google help).
• Doodle and iCloud: shared calendars added to iCloud by URL are not read (Doodle help).

How do I stop double bookings in Microsoft Bookings?

Microsoft Bookings reads staff calendars from Microsoft 365, not through a connection you set up. Check these settings for each staff member:

1. “Events on Microsoft 365 calendar affect availability” is ticked. Microsoft says it is on by default and recommends “leaving this setting on to avoid double-bookings” (Microsoft Learn).
2. The staff member is in your tenant. “Staff from outside your tenant will not be able to share free/busy information with Bookings” (Microsoft Learn).
3. The calendar is shared at “Can view when I’m busy” with people in your organization, as the troubleshooting section of the Bookings FAQ describes (Microsoft Learn).
4. The mailbox is in Exchange Online. Bookings “isn’t supported in a federated or hybrid environment” (Microsoft Learn).

In one Microsoft Q&A thread from September 2025, staff were double-booked despite Busy entries; the poster found that “some users did not have a default calendar” in Exchange Online and fixed it with PowerShell (Microsoft Q&A).

Can sync delay cause double bookings?

Yes, briefly. Microsoft says Bookings availability “is updated when the page is loaded, and when a booking is made”, and that if two people try to book the same slot, “Bookings will only let one person book that time” (Microsoft Learn). Calendly, Cal.com and SavvyCal don’t publish a sync interval in the help pages checked for this guide. If an event you just added still shows as open, reload the booking page. If it stays open, reconnect the calendar: Calendly says disconnects typically follow “a password change, revoked permissions, or a temporary connection issue” (Calendly help).

What is a quick checklist to prevent double bookings?

1. Connect every account that holds real commitments, within your plan’s calendar limit.
2. Tick each calendar under the tool’s conflict-check setting.
3. Set events, including all-day ones, to Busy.
4. Copy events from subscribed calendars onto your own calendar, or add shared calendars to your own account.
5. In Microsoft Bookings, confirm the free/busy setting, tenant membership and calendar sharing for each staff member.
6. Book a test meeting over an existing event to confirm it is blocked.

Where to compare booking tools

The comparison table lists each booking tool, free scheduling tools shows what each free plan includes, and pricing shows what more calendar connections cost.

Questions