Plan VLAN IDs, subnets and trunking assignments across switches.
VLANs (Virtual LANs, IEEE 802.1Q) split a single physical switch into multiple isolated broadcast domains, each identified by a VLAN ID from 1–4094. Planning VLAN capacity means dividing the switch's access ports (after reserving trunk/uplink ports for tagged inter-switch traffic) evenly across the number of VLANs needed, and checking that each VLAN's device count fits within its allotted ports — since every device in a VLAN shares the same broadcast domain and Layer 2 traffic isolation.
Access ports per VLAN
ports_per_vlan = floor((total_ports − trunk_ports) / number_of_vlans)
IEEE 802.1Q defines VLAN IDs from 0 to 4095, but 0 and 4095 are reserved for special use, leaving 1–4094 (4094 usable VLANs) for normal configuration. VLAN 1 is also often reserved as the default/native VLAN by convention.
Trunk ports carry tagged traffic for multiple VLANs between switches (or to a router) and aren't assigned to a single VLAN's access port pool, so they must be subtracted from the total before dividing remaining ports among VLANs.
All devices in the same VLAN share one broadcast domain — a broadcast frame (like an ARP request) is delivered to every device in that VLAN. Larger VLANs mean more broadcast traffic reaching more hosts, which can affect performance if a VLAN grows too large.
You'll need additional switches connected via trunk ports (extending the same VLANs across switches) or a higher port-density switch. The trunk link carries the VLAN-tagged traffic between switches so the VLAN's broadcast domain spans both.