By default, 75% of the interface bandwidth can be used for fancy queueing. If this percentage needs to be changed, the max reserved bandwidth command can be used to specify the amount of bandwidth being allocated to fancy queueing. The formula for calculating the Available Bandwidth is
Available Bandwidth = (max reserved bandwidth * interface bandwidth) - (sum of priority classes)
The above formula will be used only if the policy map is configured and also the policy map should be appiled to the corresponding interfaces. If the policy map is not configured then the formula for calculating the Available bandwidth is
Available Bandwidth = (max reserved bandwidth * interface bandwidth).