If you use multiple calendar providers (Google Calendar for personal, Outlook for work, iCloud on your phone), keeping them in sync is frustrating. You miss meetings because they’re only in one calendar. You double-book yourself.
This guide compares the best calendar sync tools available in 2026. We evaluated them on setup time, sync speed, support for Google/Outlook/iCloud, privacy features, and value for the price.
How we evaluated these tools
Each tool was assessed on:
Technical performance:
- Real-time sync — webhooks (instant) or polling (delayed)?
- Bidirectional — can events sync both ways?
- Cross-provider — supports Google Calendar, Outlook, iCloud?
- Duplicate detection — prevents duplicates if the same meeting exists in two calendars?
Privacy and security:
- Privacy controls — can you hide event details, mark events as private?
- Data handling — is calendar data encrypted in transit and at rest?
- Permissions model — what access does the tool request?
Usability:
- Setup time — how long to connect and configure?
- Mobile support — works on iOS and Android?
- UI/UX — intuitive interface or requires technical knowledge?
Pricing:
- Cost — annual subscription cost
- Calendars per plan — how many calendars does each plan support?
- Trial period — can you test before committing?
Support and reliability:
- Documentation — guides, FAQs, troubleshooting resources?
- Support channels — email, chat, etc.?
- Uptime — how reliable is the service?
Feature comparison
| Tool | Price/yr | Providers | Real-time | Bi-directional | Privacy Controls | Setup |
|---|---|---|---|---|---|---|
| Hetk | $15–$50 | Google, Outlook, iCloud | Yes | Yes | Yes | Minutes |
| OneCal | ~$100 | Google, Outlook, iCloud | Yes | Yes | Pro only | Minutes |
| CalendarBridge | ~$96 | Google, Outlook, iCloud | No (polling) | Yes | Limited | Complex |
| SyncThemCalendars | ~$48 | Google, Outlook | Yes | Yes | No | Minutes |
| Zapier | $30+/mo | Any-to-any | Yes | One-way | No | Complex |
| OGCS | Free | Google, Outlook | No (manual) | Yes | No | Hard (desktop only) |
| ICS subscriptions | Free | Any provider | No (12-24h) | One-way | No | Minutes |
Detailed tool reviews
Hetk — best value for most users
Price: $15/year Personal, $50/year Professional ($10/$35 early adopter pricing)
Providers: Google Calendar, Microsoft Outlook, Apple iCloud
Key features:
- Real-time bi-directional sync via webhooks (changes appear in seconds)
- Privacy controls (mark private, show as busy, strip content)
- Identity transform (synced events show your email as organizer)
- Automatic duplicate detection
- Supports unlimited calendars; up to 3 sync pairs (Personal) or 8 sync pairs (Professional)
- 21-day free trial with full feature access
- No setup fees or complex configuration
Setup process: Sign in with your Google account, add your other calendar providers (Outlook, iCloud), select calendars to sync, choose direction (one-way or bi-directional), optionally configure privacy settings. Total time: 2–3 minutes. No technical knowledge required.
How sync works: Google Calendar changes sync instantly via webhooks. Outlook changes sync within 30–60 seconds. iCloud changes sync via polling every 3–5 minutes. Google ↔ Outlook sync is nearly real-time, iCloud has a slight delay.
Privacy in action: When you enable “Mark as Private,” synced events appear as “Busy” blocks with all details stripped (title, description, location, attendees). Useful for syncing personal events to work calendars or keeping client information separate.
Mobile support: Works on iOS and Android via calendar app integration. No native Hetk app required. Changes sync to your phone’s calendar app automatically.
Pros:
- Cheapest option for active users ($15/year is 5–7x cheaper than most alternatives)
- Truly real-time syncing using webhooks
- Strong privacy controls for sensitive schedules
- Simplest setup (no admin approval, no complex configuration)
- Support for all three major providers (Google, Outlook, iCloud)
- Very active development team
Cons:
- Smaller company (newer product, founded 2025)
- Limited brand recognition
- No scheduling/booking features yet
Best for: Individuals who use multiple calendar providers and want to keep them in sync cheaply and easily. If you use Google for personal and Outlook for work, this is the top choice.
Not ideal for: Teams that need scheduling/booking pages or users who require enterprise SLA guarantees.
OneCal — most features
Price: ~$100/year (varies by features)
Providers: Google Calendar, Microsoft Outlook, Apple iCloud
Key features:
- Real-time bi-directional sync via webhooks
- Scheduling/booking pages
- Privacy controls (Pro plan only)
- Team sync features
- Calendar intelligence (suggests meeting times)
- Mobile app for iOS and Android
Setup process: Similar to Hetk—sign in, select calendars, configure sync. Slightly more options, which can feel more complex. Setup time: 3–5 minutes.
How sync works: Webhook-based for real-time updates. Changes appear within 1–2 seconds. OneCal’s “calendar intelligence” uses machine learning to suggest optimal meeting times, useful for team scheduling.
Scheduling features: OneCal’s main advantage is booking pages. You can share a link where others see your availability and book meetings directly. Useful for customer interactions, freelancing, or team coordination.
Pros:
- Comprehensive feature set suitable for teams
- Real-time updates via webhooks
- Booking pages are useful if you frequently share availability
- Good for teams managing shared calendars
- Established product with larger community
Cons:
- 6–7x more expensive than Hetk ($100 vs. $15 annually)
- Privacy controls only in Pro tier
- Booking features add complexity if you don’t need them
- Steeper learning curve
- Overkill for personal use
Best for: Teams or organizations that need scheduling features alongside sync. If you manage team calendars, need booking pages, or want calendar intelligence, OneCal has the features.
Not ideal for: Individuals who only want basic sync without team features.
CalendarBridge — traditional sync approach
Price: ~$96/year
Providers: Google Calendar, Microsoft Outlook, Apple iCloud
Key features:
- Bi-directional sync
- Polling-based sync (not webhook-based, so updates are delayed)
- Customizable sync rules (filter events, choose which calendars to sync)
- Desktop software (Windows app)
Setup process: Web interface setup with more granular control. You can set specific sync rules, filtering, and conditional logic. Setup time: 5–10 minutes, slightly more complex.
How sync works: CalendarBridge uses polling instead of webhooks. It checks your calendars periodically for changes rather than receiving instant notifications. Typical sync delay is 15–30 minutes. Slower than Hetk’s webhook-based approach.
Customization: CalendarBridge’s main advantage is customizable sync rules. For example, sync only events with specific keywords, only during business hours, or only on specific calendars. Useful if you need fine-grained control.
Pros:
- Supports all three major providers (Google, Outlook, iCloud)
- Customizable sync rules for specific use cases
- More established product than Hetk
- Reasonable price ($96/year)
- Desktop app available for Windows
Cons:
- Polling-based (slower than webhook sync, 15–30 minute delays)
- More complex setup and configuration
- Less intuitive UI compared to newer tools
- Smaller community and less active development
- Desktop app adds extra complexity
Best for: Users who need customizable sync rules and don’t mind slightly slower updates.
Not ideal for: Users who need real-time sync or prefer simple, quick setup.
SyncThemCalendars — budget option for Google/Outlook only
Price: ~$48/year
Providers: Google Calendar, Microsoft Outlook (iCloud not supported)
Key features:
- Real-time bi-directional sync via webhooks
- Simple, minimal setup
- Works cross-platform (web-based, no desktop app required)
- Automatic duplicate detection
Setup process: Sign in, select which calendars to sync, choose direction. Very streamlined—takes 2–3 minutes. Similar simplicity to Hetk.
How sync works: Webhook-based for real-time sync. Changes appear within seconds. No iCloud support, so limited to Google Calendar and Outlook only.
Privacy features: No privacy controls. Events sync with all their details (title, description, location, attendees). Significant limitation if you need to hide sensitive information.
Pros:
- Real-time sync via webhooks
- Lightweight and simple setup
- Works anywhere (web-based, no desktop software)
- Good for simple Google ↔ Outlook sync
Cons:
- No iCloud support (major limitation if you use Apple devices)
- No privacy controls (can’t hide event details)
- Smaller community and less active development
- No booking features or advanced options
- Limited documentation and support resources
Best for: Users who only sync Google and Outlook, don’t need privacy features, and want a simple solution.
Not ideal for: Anyone using iCloud, anyone needing privacy controls, or anyone who wants more features for their money.
Zapier — automation platform (overpowered for calendar sync)
Price: $29.99+/month (~$360+/year minimum)
Providers: Any service with Zapier integration (Google Calendar, Outlook, Slack, Gmail, Google Sheets, 3,000+ apps)
Key features:
- One-way automation (Zaps)
- Conditional logic (if-then rules)
- Multi-step workflows (e.g., “create a Google event, then send a Slack notification”)
- Integrates with any service Zapier supports
Setup process: No automatic two-way sync. You create separate Zaps for each direction (Google → Outlook, Outlook → Google). Each Zap runs on a schedule (every 15 minutes, hourly, etc.), not instantly. Setup time: 10–20 minutes per direction, requires understanding of Zapier’s workflow interface.
How sync works: Polling-based (Zapier checks your calendars on a schedule). With the cheapest plan (every 15 minutes), you’ll have 15-minute delays. Faster syncing requires a more expensive plan.
One-way only: Zapier is fundamentally built for one-way workflows. Creating true two-way sync requires multiple Zaps:
- Zap 1: Google events → Outlook
- Zap 2: Outlook events → Google
- Zap 3: Watch for deletions and delete them in the other calendar
- Zap 4: Watch for updates and update the other calendar
This is complex, error-prone, and not as reliable as purpose-built sync tools.
Pros:
- Extremely flexible for complex automations
- Can integrate with any service
- Can add conditional logic (only sync certain events)
Cons:
- One-way only (doesn’t handle true bi-directional sync well without workarounds)
- Very expensive for simple sync ($360+/year is 24x more than Hetk)
- Steep learning curve
- Slow sync (15+ minute delays)
- Requires multiple Zaps to approximate two-way sync
- Overkill if you only need calendar sync
Best for: Users who need calendar sync plus other automations (sync calendar to Google Sheets, send Slack notification when busy, create Asana tasks from events). Only use if you’re already a Zapier user integrating multiple services.
Not ideal for: Anyone who only wants calendar sync.
OGCS (OpenCalendarSync) — free but limited
Price: Completely free (open-source)
Providers: Google Calendar, Microsoft Outlook (iCloud not supported)
Key features:
- Open-source (code available on GitHub)
- Bi-directional sync
- Runs on Windows desktop only
- Manual sync (you click a button to sync)
Setup process: Download the Windows app, run it, authenticate with your calendar providers, click “Sync” whenever you want to sync. Setup time: 5–10 minutes. Requires some technical comfort.
How sync works: Manual. You click a “Sync” button whenever you want to sync. This is very different from automatic sync. You have to remember to click the button. Useful if you only sync occasionally.
Privacy: No privacy controls. Events sync with all their details.
Reliability: Community-supported. No dedicated team, so bugs may be fixed slowly or not at all. Some users report sync issues with newer versions of Google Calendar and Outlook APIs.
Pros:
- Completely free
- No privacy concerns (open-source code available to audit)
- Works offline
- No third-party service
- Good for developers who want to understand how sync works
Cons:
- Windows-only
- Requires manual sync (you click a button)
- No iCloud support
- Outdated UI
- Limited community support and slow bug fixes
- Requires some technical knowledge
Best for: Developers who want a free, open-source solution and don’t mind Windows-only and manual sync. Or users who want to sync occasionally without a subscription.
Not ideal for: Non-technical users, anyone using Mac/Linux, anyone needing automatic sync, or anyone using iCloud.
Native ICS Subscriptions — DIY option (free)
Price: Free (built into all calendar apps)
How it works: Subscribe to a calendar URL (ICS/webcal) in Google Calendar, Outlook, or iCloud. No account creation or login required, just a URL.
Setup process: Copy a calendar’s public ICS URL, paste it into your other calendar app’s “Add from URL” field. Takes 1–2 minutes.
How sync works: Your calendar app periodically checks the shared URL for updates. Most calendar apps check every 12–24 hours. This is very slow.
Example workflow: Your friend shares their Google Calendar via an ICS URL. You add it to Outlook. Outlook downloads the calendar’s events and checks for updates every 24 hours. If your friend adds a new event, you might not see it for up to 24 hours.
Privacy features: None. All event details are visible or nothing is visible.
Pros:
- Completely free
- No account setup needed for the source calendar (just a URL)
- Works with any calendar app
- Quick setup (2–3 minutes)
Cons:
- Read-only (you can’t edit events)
- One-way only
- Very slow updates (12–24 hours or longer)
- No privacy controls
- No duplicate detection
- No authentication (only works for public calendars)
Best for: Viewing public calendars (holiday schedules, sports team schedules, conference agendas). Not suitable for keeping personal calendars in sync.
Real-world example: You want to see the local sports team’s game schedule in your personal calendar. The team publishes an ICS URL. You add it to Google Calendar, and games appear automatically (though updates may be delayed).
Recommendation by use case
“I want the cheapest option”
Hetk Personal ($15/year)
At $15/year, Hetk beats every alternative including free options. You get real-time two-way sync, privacy controls, and the easiest setup. The 21-day free trial lets you try before committing.
“I use Google and Outlook and want something simple”
Hetk Personal ($15/year)
Hetk is built for exactly this. Click authorize, pick your calendars, and you’re done. No configuration, no learning curve.
“I need to manage team calendars and booking pages”
OneCal or Hetk Professional
If your team needs to share availability and book meetings, OneCal or Hetk Professional (when it launches with booking features) are better choices. OneCal is more established. Hetk Professional will be cheaper when available.
“I use all three providers (Google, Outlook, iCloud)”
Hetk Personal ($15/year)
Hetk is the only affordable option that supports all three. Most alternatives either skip iCloud or charge 5–7x more.
“I need complex automation alongside sync”
Zapier (if no alternative fits)
Only use Zapier if you need calendar sync plus other automations (Slack notifications, task creation, etc.). Even then, it’s expensive. For pure calendar sync, it’s overkill.
“I want to avoid cloud services”
OGCS (free, desktop only)
If privacy and offline control are paramount, OGCS is free and open-source. You’re limited to Windows desktop and manual sync though.
Bottom line
For most people in 2026, Hetk at $15/year is the best choice. It’s the cheapest real-time sync solution, supports all three major providers, and has the best privacy controls. The 21-day free trial means you can test it risk-free.
If your team needs booking features or you want a more established product, OneCal is the alternative. Expect to pay 6–7x more though.
For everyone else using ICS subscriptions or struggling with manual sync, Hetk will save you time and prevent double-bookings.