PoE Power Budget Calculator
Check a PoE switch power budget per IEEE 802.3af/at/bt. Add powered devices by type and PD class to total the watts drawn, see the utilization and headroom, and confirm the load fits the switch budget and port count. Free, no sign-up.
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Explanation
A PoE power budget is the total wattage a Power over Ethernet switch can deliver across all of its ports at once. It is not the per-port maximum multiplied by the number of ports — a 24-port switch rated for 30 W per port almost never has a 720 W budget. This calculator totals the load of the devices you connect and checks it against the switch budget per the IEEE 802.3af, 802.3at, and 802.3bt standards, then shows the utilization and how much headroom is left.
How the calculator works
There are two honest ways to total a PoE load, and this calculator does both. The choice matters because a managed switch reserves power by the device’s advertised class, not by what it actually draws.
Class reservation: P = Σ (class PSE power × quantity)
| Term | Meaning |
|---|---|
| P | Total power counted against the budget (W) |
| PSE | Power sourcing equipment — the switch; the wattage it allocates at the port |
| PD | Powered device — the camera, AP, or phone; the wattage guaranteed after cable loss |
Use actual draw when you know the real consumption of each device and the switch does not strictly reserve by class. Use PD class reservation for the conservative case a managed PSE follows — it holds the full class maximum at every port even if the device draws less. The result is Within budget below 80% utilization, Low headroom from 80–100%, and Over budget above 100%.
IEEE 802.3 PoE classes
Each powered device negotiates a class with the switch. The PSE power is what the switch must set aside at the port and is the figure that counts against the budget; the PD power is the minimum the device is guaranteed to receive after losses in up to 100 m of cable.
| Class | Standard | PSE power | PD power |
|---|---|---|---|
| 0 | 802.3af (Type 1) | 15.4 W | 12.95 W |
| 1 | 802.3af (Type 1) | 4 W | 3.84 W |
| 2 | 802.3af (Type 1) | 7 W | 6.49 W |
| 3 | 802.3af (Type 1) | 15.4 W | 12.95 W |
| 4 | 802.3at (Type 2) | 30 W | 25.5 W |
| 5 | 802.3bt (Type 3) | 45 W | 40 W |
| 6 | 802.3bt (Type 3) | 60 W | 51 W |
| 7 | 802.3bt (Type 4) | 75 W | 62 W |
| 8 | 802.3bt (Type 4) | 90 W | 71.3 W |
802.3af is PoE, 802.3at is PoE+, and 802.3bt is PoE++ (Types 3 and 4). Class 0 is the default when a device does not advertise a finer class, so the switch reserves the full 15.4 W.
Typical device power
Real draw depends on the model and its features — an IR illuminator, heater, or pan-tilt motor pushes a camera into a higher class. Confirm each value against the device datasheet; these presets are starting points.
| Device | Typical draw | Class |
|---|---|---|
| IP camera, fixed | 6 W | 2 |
| IP camera with IR / heater | 12 W | 3 |
| PTZ camera | 25 W | 4 |
| Wi-Fi access point | 12 W | 3 |
| Wi-Fi 6 / 6E access point | 25 W | 4 |
| VoIP desk phone | 6 W | 2 |
| Video phone / display | 25 W | 4 |
| Access control / card reader | 12 W | 3 |
| PoE LED light | 25 W | 4 |
| IoT sensor / small device | 3.5 W | 1 |
| PoE door lock / strike | 6 W | 2 |
Notes and limitations
Leave headroom. Cable loss means a device pulls more from the switch than it consumes at the far end, inrush current at power-up briefly exceeds the steady draw, and projects grow — so designing to about 80% of the rated budget is common practice. This tool sizes the switch power budget only; it does not size the conductors, account for cable length or gauge, or replace the manufacturer’s per-port and per-switch limits. Confirm the budget, classes, and device draw against the switch and device datasheets.