PoE Power Budget Calculator
Plan a PoE switch: add your access points, cameras, and phones and check total draw against the switch's power budget. Standard 802.3af/at/bt wattages. Free.
On the switch datasheet as "PoE power budget" — often less than ports × 30 W.
Wattages are typical PSE-side draw; a switch may reserve the full class allocation (up to 30 W for 802.3at, 60–90 W for 802.3bt) per port regardless of actual draw, so leave ~20% headroom. Long or thin cable runs add loss the switch must also supply.
PoE standards and per-port power
A switch's total PoE power budget is almost always less than the sum of what every port could deliver. A 24-port switch might advertise 802.3at (30 W) on every port but carry only a 370 W budget — enough for about 12 full-power devices, not 24. That's the number this calculator checks against.
| Standard | Name | PSE (switch) max | PD (device) max |
|---|---|---|---|
| 802.3af | PoE (Type 1) | 15.4 W | 12.95 W |
| 802.3at | PoE+ (Type 2) | 30 W | 25.5 W |
| 802.3bt | PoE++ (Type 3) | 60 W | 51 W |
| 802.3bt | PoE++ (Type 4) | ~90–100 W | 71.3–90 W |
The gap between PSE and PD figures is cable loss — the switch has to source more than the device receives, and that difference grows with run length and thinner cable. New to speccing PoE for cameras and access points? See PoE switch basics for IP cameras and access points.