Can I hide the duration from customers and still block that time in my calendar?

There is no switch to hide the duration: the website and the widget show the service duration (plus the wait time, if it has one). What you can do is block more time in your calendar than the customer sees.

Block extra time without showing it

1. Go to My Business → Resources & Services and edit the service.
2. Open “Additional timing” and enter the minutes in “Gap between appointments (min)”.
3. Save the service.

The gap is added at the end of each appointment and the resource is not freed during that time, so bookings don’t overlap. The website and the widget don’t show it.

Explain the duration to customers

If you want to make clear that the duration is approximate, write it in the service’s “Description (optional)”, which shows on your website, or in “Customer instructions” (under the service’s “Advanced settings”), which appear at the bottom of the confirmation, reminder and update emails.