1. Enter the switch model, its total PoE budget in watts (from the datasheet, not the power-supply rating) and the number of PoE ports.
2. Pick the port standard: 802.3af, 802.3at (PoE+), or 802.3bt Type 3 / Type 4. This sets the per-port limit.
3. Add one row per device type. Choose a preset or type the device's maximum power from its datasheet, and set the quantity.
4. Leave Class on Auto or set the class printed on the datasheet. A device that draws more than its class allows is flagged.
5. Enter the cable length and cable type for each row. Cable loss is added to give the power the switch must supply.
6. Choose Calculate by: device max power, or class allocation if your switch reserves power by class.
7. Read the KPIs and verdict. Keep the load inside the green zone of the budget bar, then save, export or print the result.

Tips & common mistakes

• Use the camera's max power with IR LEDs and heater on. Night-time IR and cold-start heaters are where budgets fail.
• The PoE budget is often far below the PSU rating: a "250 W" switch may only have 190 W for PoE. Check the datasheet.
• Copper-clad aluminium (CCA) cable has about 1.6× the resistance of copper. It increases loss and is not standards-compliant for PoE.
• A 60 W heater PTZ needs an 802.3bt Type 4 port (or a midspan/injector). It will not run on PoE+.
• Over 100 m, use a PoE extender or a fibre link with a local PoE switch.

Standards & assumptions

IEEE 802.3af-2003, 802.3at-2009 and 802.3bt-2018 (now part of IEEE 802.3) PSE and PD class powers; ANSI/TIA-568 and ISO/IEC 11801 (100 m channel, 90 m permanent link). Cable loss is P = I²R at the minimum PSE voltage (44 V af, 50 V at/bt Type 3, 52 V bt Type 4), with conductor DC resistance at 20 °C of 9.38 Ω/100 m for 24 AWG (TIA maximum) and 7.33 Ω/100 m for 23 AWG (typical). 2-pair powering is assumed up to Class 4 and 4-pair for Classes 5–8. Per-pairset current limits of 350 / 600 / 600 / 960 mA are typical. Higher temperatures and bundled cables increase resistance. Device powers in the presets are typical; use your datasheet. The result is for guidance only and must be verified against the manufacturer's data and local code.