Best calendar sync tools in 2026: 9 compared

A calendar sync tool copies events from one calendar account onto another and keeps the copies current, so every calendar shows the same busy times. These nine do that job, compared here on price, free plan, update speed and which calendars they connect. Keeper.sh, which publishes this comparison, is the pick for people with work and personal calendars on different providers: it connects Google Calendar, Outlook, iCloud, Fastmail and any CalDAV server. It is free for 2 calendar accounts and 3 connections, and Pro is $5 a month for unlimited calendars.

Figures for other tools come from each tool's own website, linked beside them, and were checked on 10 November 2026.

The nine calendar sync tools and who each suits

Keeper.sh is best for calendars split across providers that also need to be shared as one feed. It publishes a shareable calendar link that combines the calendars you choose into one feed whose events read "Busy" by default, and the Free plan includes 1.
SyncDate is best for two-way sync with rules. One sync can run two-way or one-way, and paid plans add rules by event length, weekday and guest domain. Its free plan covers 2 accounts and 1 sync, and Plus is $10 a month billed yearly (SyncDate alternative).
OneCal is best for people who want sync, scheduling links and one calendar view in the same product. It has iOS and Android apps and an AI assistant, and Starter is $5 per user a month billed annually for 2 calendars (OneCal alternative).
CalendarBridge is best for healthcare and government teams. It signs a HIPAA business associate agreement on its Premium and Pro plans, holds SOC 2 Type 1 and Type 2 reports, and supports Microsoft 365 GCC High. Basic is $5 a month, or $4 a month billed yearly (CalendarBridge alternative).
SyncThemCalendars is best for choosing exactly which fields of a copy to hide: any field can be hidden behind "Busy", and each sync can run both ways or one way between Google Calendar, Outlook and iCloud. Basic is $3.99 a month billed yearly, or $4.99 a month billed monthly, for 5 calendar syncs (SyncThemCalendars alternative).
Kalender Sync is best for German mailbox providers. GMX, WEB.DE, Posteo, mailbox.org and STRATO are named integrations, a data processing agreement is part of the terms on every plan, and Basic is €5 a month, or €50 a year (Kalender Sync alternative).
CalendarSync is best for a small team that wants sync and scheduling links in one product. Its Team plan is $6 per user a month for up to 25 members, with unlimited syncs and scheduling links, and its free plan covers 2 calendar accounts, 1 sync configuration and 1 scheduling link.
Reclaim.ai is best for people who want AI scheduling of tasks, habits and focus time alongside sync between Google Calendar and Outlook. Its free Lite plan includes 1 Calendar Sync, and Starter is $10 per seat a month billed yearly (Reclaim.ai alternative).
OGCS (Outlook Google Calendar Sync) is best for syncing Outlook with Google Calendar from a Windows PC at no cost. It is a free desktop app that copies attendees, reminders and full descriptions, and it syncs as often as every 15 minutes (OGCS alternative).

Price, free plan, calendars and speed

The table lists each tool's lowest paid price, what its free plan or trial covers, the calendars it connects and its published update speed.

Tool Entry price Free plan Calendars Update speed

Keeper.sh $5/month, or $45/year Yes: 2 calendar accounts and 3 connections, no card needed Google Calendar, Outlook, iCloud, Fastmail, any CalDAV server; .ics links read-only Pro: Google and Outlook within seconds, iCloud, Fastmail and CalDAV every minute. Free: every 30 minutes

SyncDate $10/month billed yearly Yes: 2 accounts, 2 calendars, 1 sync, copies 30 days ahead Google Calendar, Outlook, iCloud, Fastmail, Nextcloud, any CalDAV server; ICS links read-only Google and Outlook "Usually in under a minute"; iCloud and CalDAV "Checked about every 15 minutes"

OneCal $5/user/month billed annually, 2 calendars No: 14-day trial, no card Google Calendar, Outlook, iCloud, any CalDAV server "in real-time", no figure published; iCloud and CalDAV up to 10 minutes

CalendarBridge $5/month, or $4/month billed yearly No: 7-day trial, no card Google Calendar, Microsoft 365 for Business, Microsoft personal accounts, iCloud; .ics links Google and Outlook in real time; iCloud and .ics links every 5 to 10 minutes

SyncThemCalendars $3.99/month billed yearly, or $4.99/month, 5 calendar syncs No: 14-day trial, no card Google Calendar, Outlook, iCloud "in real time", no figure published

Kalender Sync €5/month, or €50/year Yes: 2 calendar accounts and 1 sharing with another person Google Calendar, Outlook, iCloud, GMX, WEB.DE, Posteo, mailbox.org, STRATO, Disroot, Infomaniak kSuite; iCal feeds read-only Google and Outlook by webhook; iCloud about every 5 minutes

CalendarSync $5/month, or $50/year Yes: 2 calendar accounts, 1 sync configuration, 1 scheduling link Google Calendar, Outlook, iCloud "Changes propagate instantly via webhooks", no figure published

Reclaim.ai $10/seat/month billed yearly Yes: Lite, with 1 Calendar Sync Google Calendar and Outlook "in real-time", no figure published

OGCS Free Yes: the whole app is free Outlook and Google Calendar Every 15 minutes at the fastest; Outlook edits within 2 minutes with push turned on

Tool	Entry price	Free plan	Calendars	Update speed
Keeper.sh	$5/month, or $45/year	Yes: 2 calendar accounts and 3 connections, no card needed	Google Calendar, Outlook, iCloud, Fastmail, any CalDAV server; `.ics` links read-only	Pro: Google and Outlook within seconds, iCloud, Fastmail and CalDAV every minute. Free: every 30 minutes
SyncDate	$10/month billed yearly	Yes: 2 accounts, 2 calendars, 1 sync, copies 30 days ahead	Google Calendar, Outlook, iCloud, Fastmail, Nextcloud, any CalDAV server; ICS links read-only	Google and Outlook "Usually in under a minute"; iCloud and CalDAV "Checked about every 15 minutes"
OneCal	$5/user/month billed annually, 2 calendars	No: 14-day trial, no card	Google Calendar, Outlook, iCloud, any CalDAV server	"in real-time", no figure published; iCloud and CalDAV up to 10 minutes
CalendarBridge	$5/month, or $4/month billed yearly	No: 7-day trial, no card	Google Calendar, Microsoft 365 for Business, Microsoft personal accounts, iCloud; `.ics` links	Google and Outlook in real time; iCloud and `.ics` links every 5 to 10 minutes
SyncThemCalendars	$3.99/month billed yearly, or $4.99/month, 5 calendar syncs	No: 14-day trial, no card	Google Calendar, Outlook, iCloud	"in real time", no figure published
Kalender Sync	€5/month, or €50/year	Yes: 2 calendar accounts and 1 sharing with another person	Google Calendar, Outlook, iCloud, GMX, WEB.DE, Posteo, mailbox.org, STRATO, Disroot, Infomaniak kSuite; iCal feeds read-only	Google and Outlook by webhook; iCloud about every 5 minutes
CalendarSync	$5/month, or $50/year	Yes: 2 calendar accounts, 1 sync configuration, 1 scheduling link	Google Calendar, Outlook, iCloud	"Changes propagate instantly via webhooks", no figure published
Reclaim.ai	$10/seat/month billed yearly	Yes: Lite, with 1 Calendar Sync	Google Calendar and Outlook	"in real-time", no figure published
OGCS	Free	Yes: the whole app is free	Outlook and Google Calendar	Every 15 minutes at the fastest; Outlook edits within 2 minutes with push turned on

How Keeper.sh syncs calendars

Keeper.sh is a calendar sync service that copies events between Google Calendar, Outlook, iCloud, Fastmail and any CalDAV server. Each copy is a busy block named after the source calendar. The title, description and location are hidden by default, Pro can turn them back on per calendar, and guest lists are never copied. Each connection runs one way, so two-way sync is two connections; the calendar sync features page lists what else each connection can do. The Free plan covers 2 calendar accounts and 3 connections, with changes landing every 30 minutes. Pro is $5 a month or $45 a year, with Google and Outlook changes landing within seconds and iCloud, Fastmail and CalDAV changes landing every minute (pricing).

Google and Outlook connect by signing in, iCloud with an app-specific password and Fastmail with an app password. Create a Keeper.sh account to connect the first two calendars; the Free plan needs no card.

For the mechanics behind any of these tools, see what calendar sync is. Step-by-step setup is in how to sync Google Calendar and Outlook, how to sync iCloud and Google Calendar and how to sync iCloud Calendar with Outlook.

Calendar sync tools with an MCP server

Keeper.sh, SyncDate, OneCal, CalendarBridge and Kalender Sync each publish an MCP server, the connector that lets an AI assistant such as Claude or ChatGPT read and change a calendar.

Keeper.sh: the server is hosted at https://www.keeper.sh/mcp and signs in with OAuth 2.1 and a consent screen, with no API key. Its tools are listed in the Keeper.sh MCP reference, and the Free plan includes 25 API and MCP calls a day.
SyncDate: Platform MCP is on every plan, and Calendar Hub MCP, which works with calendar events, is on Plus, Pro and Team.
OneCal: the OneCal Calendar MCP Server covers Google Calendar, Outlook and iCloud calendars connected to OneCal.
CalendarBridge: connecting an agent is available on every plan, and actions need an active subscription.
Kalender Sync: MCP is included on all plans.

Calendly and Morgen: a booking tool and a calendar app

Calendly is a booking tool. It "checks your calendar for busy times and adds new meetings to it"; its free plan connects 1 calendar and its paid plans connect up to 6 per user. A calendar sync tool copies the busy time from every other calendar onto one Calendly checks; how to stop Calendly double-booking has the steps. Calendly with Keeper.sh covers checking more calendars than a Calendly plan connects.
Morgen is a calendar app for desktop and phone with task integrations and daily planning. Its calendar blocking workflow runs daily at 6pm, or when you run it by hand, and covers the upcoming 14 days (Morgen alternative).

Common questions about calendar sync tools

Which calendar sync tools have a free plan?

Keeper.sh, SyncDate, Kalender Sync, CalendarSync and Reclaim.ai have a free plan, and OGCS is free desktop software. Keeper.sh's Free plan covers 2 calendar accounts and 3 connections, SyncDate's covers 2 accounts and 1 sync, Kalender Sync's covers 2 calendar accounts and 1 sharing with another person, CalendarSync's covers 2 calendar accounts and 1 sync configuration, and Reclaim.ai's Lite plan includes 1 Calendar Sync between Google Calendar and Outlook.

Which calendar sync tools work with iCloud?

Keeper.sh, SyncDate, OneCal, CalendarBridge, SyncThemCalendars, Kalender Sync and CalendarSync connect iCloud calendars. Reclaim.ai's Calendar Sync supports Google and Outlook accounts, and OGCS syncs Outlook with Google Calendar.

How fast do calendar sync tools update?

Tools that receive change notifications from Google and Outlook update fastest: within seconds on Keeper.sh Pro, and usually in under a minute on SyncDate. iCloud and CalDAV calendars are checked on a timer: every minute on Keeper.sh Pro, every 5 to 10 minutes on CalendarBridge, up to 10 minutes on OneCal and about every 15 minutes on SyncDate.

Does Keeper.sh do two-way sync?

Yes. Keeper.sh sets up two-way sync as two connections, one in each direction. A two-way pair uses 2 accounts and 2 connections, which fits the Free plan with one connection spare.

Can a calendar sync tool stop double-booking through Calendly or another booking tool?

Yes. A booking tool blocks only the times that are busy on the calendars it checks. Keeper.sh copies events from your other calendars onto that calendar as busy blocks, so the booking tool stops offering those times.

Will colleagues see private event details on a synced copy?

No, not by default. A Keeper.sh copy is a busy block named after the source calendar, with the title, description and location hidden, and guest lists are never copied on any plan.