The number of sync connections you need is driven by how many calendars you want to sync and in which direction(s) you want to sync them.

To illustrate, here are two common configurations involving 3 calendars X, Y, and Z (these calendars may reside on 1, 2, or 3 Google/Microsoft/iCloud accounts):

- Copying events from X to Y and from Z to Y requires 2 sync connections (X->Y, Z->Y).
- With this configuration, X will not sync to Z, Z will not sync to X, and Y will not sync to either of X and Z.

- Copying events from each of X, Y, and Z to each other of X, Y, and Z requires 6 sync connections (X->Y, X->Z, Y->X, Y->Z, Z->X, Z->Y).

**Thus…**

**If you only have 2 calendars**, you definitely only need a Basic license.

**If you have 3 calendars**, then you probably need a premium plan…

- If you want each of the 3 calendars to reflect all 3 calendars (this is most common), then you need 6 sync connections (A->B, B->A, A->C, C->A, B->C, C->B).
- If you tried to make do with a basic license by doing, for example, B->A and C->A, then:
- A would reflect availability of all three calendars,
- B would only reflect B
- C would only reflect C.
- Thus, basic would not work for you if other people are checking your availability on calendar B or calendar C.

**If you have 4 calendars**, you definitely need premium.

**If you have 5 or 6 calendars**, you probably need pro, but you could possibly get away with premium if you don’t need all calendars reflecting all other calendars (similar to the example above for 3 calendars).

**If you have 7 or more calendars**, there is no way on an individual account to have all calendars reflect all 6 other calendars.

For more information, see Setting up Calendar Syncing