A method, system, and computer program product for providing VLAN capacity requirement estimation is provided. The method includes receiving at a computing system a VLAN configuration file that specifies VLAN access ports, VLAN switches and VLAN trunks in a VLAN. A target access port identifier is received at the computing system from a requestor. A target trunk and target switch corresponding to the target access port are determined at the computing system. A bandwidth contribution of the target access port to the VLAN is calculated at the computing system. The calculating is based on a least contribution algorithm that reflects an impact of provisioning the target access port with respect to trunk capacity, and is responsive to the target bandwidth requirement, the target class of service and placement of the target port in the VLAN. The bandwidth contribution is then transmitted to the requestor.