First things first: do you really need to sync Google and Outlook calendars? You might think you do, but there are several alternative approaches which might solve your problem. For example, if you have an iPhone, Android phone or just about any other smartphone, you should be able to add multiple accounts (and therefore multiple calendars) in the settings and have Google and Outlook calendars appear together in the same app.
If you don't have a phone, or your problem is on your PC and you're still using the Outlook application in Windows, it could be time to ditch it and move to the online version, Outlook.com, which supports multiple calendars. There are several other advantages of using an online email / calendar service: you can log on from any computer with an internet connection, and you don't have any synching issues as everything is stored online.
How to Sync Google and Outlook Calendars: pick just one
Using two calendars services from two different companies can lead to problems and it's worth considering using only one, if at all possible. We understand that it's useful to use multiple email providers, but when it comes to your calendar, why not just pick one and use just that?
It simplifies scheduling appointments and events and solves the whole sync problem. Both Google and Microsoft support multiple calendars, such as work and private, and offer single calendar or combined views. (This applies whether you're using a mobile device or a PC or laptop, by the way.)
When adding a new event, you can choose which calendar to add it to. This is the only complication, as it's all too easy to add an event to the wrong calendar. But at least you'll have no problems with synching.
To use Google or Outlook, just export one and import it into the other. For example, to export Google Calendar click the drop-down menu next to the relevant calendar in the My Calendars section on the left and choose Calendar Settings. Then scroll down and click Export this calendar. It downloads as a zip, so copy the .ics file out.
To import this into Outlook, go to File, Open and export, Import and export. Select the option to import an iCalendar (.ics) file.
To export your Outlook calendar, go to File, Open and export, Import and export. Select Export to a file and save it to a .csv file. To import it into Google Calendar, click the down arrow next to Other calendars and select Import calendar.
If you use Outlook.com Calendar, just click Import in the menu and select the Google Calendar .ics file to import it. To export to Google Calendar is more difficult. Click the Share menu, then Get a link. Select the ICS URL with the mouse and press Ctrl+C. Go to Google Calendar, click the down arrow next to Other Calendars and select Add by URL. Press Ctrl+V to paste in the URL you copied, but replace webcals:// at the start with http://.
All your Outlook events and appointments are now either in Google Calendar, whichever one you chose to import to and the sync problems are over.
How to Sync Google and Outlook Calendars: View both calendars
On an Android phone or tablet, install the free Microsoft Outlook app from the Google Play Store. (You can't simply add a Microsoft or Outlook account in the Android 'add account' setting, unfortunately. You can try adding an Exchange account, but it doesn't work with all Microsoft accounts.)
The Outlook app includes your Outlook.com calendar and merges it with the one on the device. This means that no matter which calendar an appointment or event is added to, it appears in the Android Calendar app. It does not sync calendars and make them identical, it just looks that way and the Android app can read Outlook.com Calendar, but not write to it.
The iPhone and iPad can display a combined Google Calendar and Outlook Calendar too. Go to Settings, Mail, Contacts, Calendars and tap Add Account. Use the options to add Google and Outlook.com accounts. Accept the offer to sync calendars and that’s it. Events added to Google Calendar, Outlook.com Calendar or Outlook if it’s synced with Outlook.com, automatically appear in the iOS Calendar app.
How to Sync Google and Outlook Calendars: invitations
One way to make an appointment appear in both Google and Outlook calendars simultaneously is to simply invite yourself by entering your email address when creating a new event. You basically create a meeting with yourself, so in Google Calendar you would invite yourself by adding your Outlook or Outlook.com email address.
Outlook adds a calendar invitation from Google as an unconfirmed event. You can leave it like this or click the Accept button in the email to confirm it. Outlook.com does not automatically add invitations to the calendar and you have to click Accept in the email.
You can manually accept emailed invitations sent from Outlook/Outlook.com to Google Calendar in Gmail, but there is a better way. Click the gear button in Google Calendar and selecting Settings. On the General tab is an option to automatically add invitations to your calendar.
How to Sync Google and Outlook Calendars: third-party tools
If you don’t want to use invitations to sync calendars, there are utilities that sync Google and Outlook calendars.
gSyncit v4 is a $19.99 Outlook add-in that enables one and two way syncing between Outlook and Google calendars. Sync2 (image below) syncs Outlook with Google Calendar and does a lot more besides for £29.95. It can sync on a schedule or whenever a change in Outlook is detected. OggSync does a similar job and v8.1 fixes sync problems introduced by changes at Google, but costs $29.95 a year.
Yet another option is Scand Outlook4Gmail which syncs your Outlook calendar with your Google calendar. It can also sync contacts and a single licence costs $28.98.
Calendar Sync appears to be the perfect replacement for the old Google sync tool for Outlook users. It’s a free app that is very easy to use and does exactly what you want. Enter your Google username and password and click Save Settings. Click Sign in to Google at the bottom to authorise it. Now you can select the Google calendar to sync, if there is more than one, and whether Google or Outlook is the master calendar. A two-way sync by last modified date is possible and you can choose to delete duplicates in Outlook or Google. The Auto Sync tab enables you to sync automatically, but don’t sync too often because Google imposes limits.
Some people like Calendar Sync, while others says it causes problems.
Read next: 11 ways to use Google Calendar like a pro