TradesHow this works
Power over Ethernet has to do two things at once: source enough power at the switch, and still deliver enough at the far end after the cable takes its cut. This tool picks the PoE type your device needs from its wattage, then estimates the loss and the voltage at the device over your run, and tells you whether it holds up inside the 100 meter limit.
On a long or thin run the loss is what bites, so the fixes are heavier Cat6 conductors, a shorter home run, or a midspan injector near the device. Confirm the device draw and the whole-switch PoE budget on the datasheets before you commit.
Common questions
Which PoE standard do I need?
It is set by the power your device draws. Type 1 (802.3af) guarantees 12.95 W at the device, Type 2 (802.3at) 25.5 W, Type 3 (802.3bt) 51 W, and Type 4 90 W at the switch for 71.3 W at the device. Pick the smallest type that covers your device, then make sure the switch or injector sources it.
Why does cable length matter for power?
Copper has resistance, so some of the power turns to heat on the way to the device, and the voltage sags. The PoE standard already limits the channel to 100 meters and guarantees the device power at that worst case, but long thin runs get tight, which is why Cat6 or an injector near the device helps.
What is the switch PoE budget?
Each switch has a total watt budget shared across all its PoE ports, separate from what any one port can source. A switch might do Type 3 on a port but run out of total budget if every port is loaded. Always check the whole-switch number, not just the per-port capability.
Sources: IEEE 802.3af/at/bt PoE power classes (PSE vs guaranteed PD watts), 100 m channel limit; cable DC resistance from AWG tables. Voltage drop is an estimate; verify device draw + switch budget on datasheets.. Engine version 1.0.0. Risk tier 2.