How it works
A PoE switch has a total power budget shared across its ports, and each port is limited by the PoE standard it supports. The power available at the device is lower than at the switch port because some is lost in the cable.
Enter each device's maximum draw. The calculator adds a safety margin, compares the total with the switch budget and flags any device that needs a higher PoE class than the switch provides.
Total = Σ device power × (1 + margin)
Per-port limit at device: 802.3af 12.95 W · 802.3at 25.5 W · 802.3bt Type 3 51 W · Type 4 71.3 WWorked example
Three cameras at 6.5 W, two access points at 12 W and a PTZ camera at 25 W total 68.5 W, or 75.4 W with a 10% margin. A 120 W switch has 44.6 W left, but the 25 W PTZ needs an 802.3at (PoE+) port.