Arsenal / Power planning

PoE Budget Calculator

Ports are cheap. Watts are not.

Pick a switch, add the access points, cameras and phones you plan to plug in, and see whether the power budget, the per-port standard and the cable can carry them.

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01 / The switch (PSE)

Switch power

Switch model (example budgets)

PoE budget (W)

PoE ports

Highest standard each port supports

How the switch reserves power Class-based: reserve the full PSE wattage of each device's class Actual draw: device watts plus estimated cable loss (LLDP / dynamic)

Typical cable run (feet)

02 / Powered devices (PD)

Devices

Add a device

Device watts are typical example values for practice. Always check the datasheet's maximum draw and PoE class.

Device	Needs	Draw at device (W)	Qty	Budget used	Remove

03 / Budget check

Total vs budget

Allocated

0 W

Budget

0 W

Headroom

0 W

Ports used

04 / Explainer

PSE vs PD, and where the watts go

PSE (power sourcing equipment) is the thing that supplies power: a PoE switch or a midspan injector. PD (powered device) is the thing that uses it: an access point, IP camera or VoIP phone.

The PSE number is what leaves the switch port. The PD number is the most a device is guaranteed to receive at the far end of a full-length cable. The difference is lost as heat in the copper.

The worst case assumes a 328 feet (100 meters) channel, the Ethernet maximum. Shorter runs lose less, which is why switches that read the device's real needs over LLDP can fit more devices into the same budget.

When a switch runs out of budget, it stops powering the lowest-priority ports. Set port priority on the APs and cameras you can't afford to lose.

Standard	PSE (port)	PD (device)	Worst-case loss	Pairs

802.3bt Type 3 can deliver up to 60 W using two or four pairs; Type 4 always uses all four pairs. Many vendors market Type 4 as “PoE++” or “UPoE+.” Nominal voltage is about 48 V DC.

PoE classes (what the device asks for)

Class	PSE allocation	PD maximum	Standard
0 (default)	15.4 W	12.95 W	802.3af (Type 1)
1	4 W	3.84 W	802.3af (Type 1)
2	7 W	6.49 W	802.3af (Type 1)
3	15.4 W	12.95 W	802.3af (Type 1)
4	30 W	25.5 W	802.3at (Type 2)
5	45 W	40 W	802.3bt (Type 3)
6	60 W	51 W	802.3bt (Type 3)
7	75 W	62 W	802.3bt (Type 4)
8	90 W	71.3 W	802.3bt (Type 4)

Sources: IEEE 802.3af/at/bt power levels as summarized by the Ethernet Alliance 802.3bt overview and TI/Microchip PoE design notes. Class-based mode in this tool reserves the PSE value of the device's standard (15.4 / 30 / 60 / 90 W); real switches may reserve by the exact class (for example 7 W for a Class 2 phone). Cable loss in actual-draw mode is a simple linear estimate scaled from the worst case at 328 feet (100 meters).