Power

PoE Budget

Add up how much power your switch reserves for each PoE device (by 802.3 class) and check whether the budget and ports are enough. All the math runs in your browser.

redzilla.cl — poe

Budget utilization

0 / 0 W 0%

Required (PSE)

0 W

power the switch reserves

Budget

0 W

switch PoE budget

Margin

0 W

available

PoE ports

0 / 0

used / available

Delivered (PD)

0 W

usable power at the devices

Utilization

required / budget

Breakdown by device

Device	Class / standard	Qty	PSE/ea	Total PSE	Total PD

Reference · IEEE 802.3 classes

Class	Standard	PSE reservation	Max. PD
Class 0	802.3af	15.4 W	12.95 W
Class 1	802.3af	4 W	3.84 W
Class 2	802.3af	7 W	6.49 W
Class 3	802.3af	15.4 W	12.95 W
Class 4	802.3at (PoE+)	30 W	25.5 W
Class 5	802.3bt (PoE++)	45 W	40 W
Class 6	802.3bt (PoE++)	60 W	51 W
Class 7	802.3bt (PoE++)	75 W	62 W
Class 8	802.3bt (PoE++)	90 W	71.3 W

Type 1 = 802.3af (PSE 15.4 W) · Type 2 = 802.3at / PoE+ (30 W) · Type 3/4 = 802.3bt / PoE++ (60 / 90 W).

Runs locally in your browser · no sign-up · nothing leaves your browser.

How it works

The calculator adds up the power your switch must reserve for each PoE device according to its IEEE 802.3 class (af/at/bt) and compares it against the total PoE budget of the switch. It shows the required power on the PSE side (the switch), the power actually delivered on the PD side (the device), the available margin, the utilization percentage and whether the ports are enough, with a warning when usage exceeds 85%.

The criterion is safe sizing: each port reserves the power of the negotiated class, not the actual consumption of the device. Per-class values follow the standards: Class 0/3 reserves 15.4 W (802.3af, PoE), Class 4 reserves 30 W (802.3at, PoE+) and Classes 5 through 8 reserve 45 to 90 W (802.3bt, PoE++). The gap between PSE and PD is cable loss: for example, of the 30 W of Class 4, about 25.5 W reach the device.

Example: 12 phones and 6 APs on a 370 W switch

12 Class 2 IP phones reserve 12 × 7 W = 84 W on the PSE side.
6 Class 4 WiFi 6 APs (PoE+) reserve 6 × 30 W = 180 W.
Total required: 84 + 180 = 264 W out of a 370 W budget: 71.4% usage and a 106 W margin, with 18 of 24 ports in use.

Frequently asked questions

How many PoE cameras can a 370 W switch power?

It depends on the camera class: with Class 3 (15.4 W reserved) it fits 24; with Class 4 / PoE+ (30 W) it fits 12; with Class 6 PTZ cameras (60 W) only 6. The limit is almost always the watt budget before the port count.

What is the difference between PoE, PoE+ and PoE++?

They are generations of the IEEE 802.3 standard: PoE (802.3af) delivers up to 15.4 W per port on the switch side, PoE+ (802.3at) up to 30 W, and PoE++ (802.3bt) up to 60 W in Type 3 or 90 W in Type 4. A higher-class device connected to a previous-generation switch will not receive all the power it needs.

Why does the device receive fewer watts than the switch reserves?

Because part of the power is lost as heat in the copper cable. The standard accounts for this: of the 30 W a PoE+ port reserves, about 25.5 W are guaranteed at the device, and of the 90 W of Class 8, about 71.3 W arrive. That is why the calculator distinguishes PSE (reserved) and PD (delivered) power.

What happens if I exceed the PoE budget of the switch?

The switch cannot deliver infinite power: once over budget, it will stop powering ports (usually by priority or connection order) and some devices will shut down or reboot intermittently. The calculator flags an overload when the requirement exceeds the budget and recommends staying below 85% usage.

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Disclaimer

We take great care to keep every tool accurate and review it thoroughly; even so, we can't guarantee it is free of errors or take responsibility for how the results are used. We recommend double-checking anything critical.

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