PoE Class Power Budget Calculator

August 31, 2026

PoE Class Power Budget Calculator

Model a PoE switch power budget from IEEE class allocation, PD class mix, cable loss, reserved capacity, simultaneous draw, redundancy derating, port count, and installed PSU capacity.

1PoE deployment presets

2Switch, class mix, and margin inputs

PoE standard Caps the supported PD classes and single-port allocation.

Class for remaining-port estimate Used to estimate how many more ports fit in the remaining budget.

PSE budget watts The switch PoE budget, separate from packet switching power.

PoE port count Total ports that can source power.

PD class mix profile Loads editable device counts by IEEE class.

Average cable length m Used with cable loss percent to flag long-run margin.

Cable loss percent Expected pair loss from heat, length, gauge, and current.

Reserve percent Capacity kept aside for boot surges, LLDP changes, and future devices.

Simultaneous draw percent Expected percent of PD-side class maximum being used at the same time.

Redundancy mode Derates installed PSU capacity before reserve is applied.

Switch PSU capacity watts Installed power supply capacity available to the switch chassis.

Non-PoE switch load watts ASIC, fans, uplinks, and management draw before PoE loads.

Class 0 count15.4 W

Class 1 count4 W

Class 2 count7 W

Class 3 count15.4 W

Class 4 count30 W

Class 5 count45 W

Class 6 count60 W

Class 7 count75 W

Class 8 count90 W

PoE class power budget result

Budget Used - class allocation at PSE -

Remaining Budget - after PSU derate and reserve -

Ports Filled - used PoE ports -

Cable Loss - estimated watts in cable -

Enter a class mix and calculate.

3Live budget quick cards

-Raw PoE budget

-Usable after reserve

-Expected PSE draw

-More selected ports

4PoE class comparison grid

Class 0 Type 115.4 W PSEDefault classification for older or unclassified 802.3af devices, up to 12.95 W at the PD.

Class 1 Type 14 W PSELow-power sensors, small phones, simple adapters, and lightweight endpoints.

Class 2 Type 17 W PSESmall cameras, access readers, intercoms, and compact controller boards.

Class 3 Type 115.4 W PSECommon ceiling APs, fixed IP cameras, thin clients, and home lab edge devices.

Class 4 Type 230 W PSEPoE plus APs, pan-tilt cameras, video phones, and higher-radio wireless gear.

Class 5 Type 345 W PSEFour-pair devices needing more than PoE plus but less than full 60 W allocation.

Class 6 Type 360 W PSE802.3bt APs, lighting controllers, thin terminals, and small network appliances.

Class 7 Type 475 W PSEHigh draw displays, PTZ cameras with heaters, access equipment, and bridges.

Class 8 Type 490 W PSEMaximum standard PoE allocation, up to about 71.3 W available at the PD.

5IEEE PoE reference tables

IEEE PoE standards and power limits

IEEE standard	PoE name	Type	Max PSE power	Max PD power	Supported classes
802.3af	PoE	Type 1	15.4 W	12.95 W	0 to 3
802.3at	PoE plus	Type 2	30 W	25.5 W	0 to 4
802.3bt Type 3	PoE plus plus	Type 3	60 W	51 W	0 to 6
802.3bt Type 4	High-power PoE	Type 4	90 W	71.3 W	0 to 8

IEEE class allocation table

Class	PSE allocation	Power at PD	Minimum type	Typical home lab device
0	15.4 W	0.44 to 12.95 W	Type 1	Legacy or unclassified endpoint
1	4 W	0.44 to 3.84 W	Type 1	Sensor, small phone, relay
2	7 W	3.84 to 6.49 W	Type 1	Small camera, intercom
3	15.4 W	6.49 to 12.95 W	Type 1	Fixed camera or Wi-Fi AP
4	30 W	12.95 to 25.5 W	Type 2	PoE plus AP, video phone
5	45 W	25.5 to 40 W	Type 3	Four-pair AP or terminal
6	60 W	40 to 51 W	Type 3	802.3bt AP or appliance
7	75 W	51 to 62 W	Type 4	PTZ camera with heater
8	90 W	62 to 71.3 W	Type 4	High-power display or bridge

Type, pair use, and planning notes

Type	Pairs used	Nominal cable limit	Planning note	Budget behavior
Type 1	2 pairs	100 m	Works with standard structured cabling.	Budget usually reserves by class.
Type 2	2 pairs	100 m	Higher current, more heat than Type 1.	Watch bundles and warm spaces.
Type 3	4 pairs	100 m	Shares current across four pairs.	Requires 802.3bt-capable PSE and PD.
Type 4	4 pairs	100 m	Highest standard power class.	PSU and thermal reserve matter most.

Common PoE deployment sizing patterns

Deployment	Likely class mix	Useful switch type	Watch item	Calculator setting
Small home AP and cameras	Class 2 to 4	8 to 16 port PoE plus	AP boot spikes	10 to 15% reserve
NVR camera cabinet	Mostly Class 3	16 port PoE plus	Night IR draw	80 to 90% draw
Wi-Fi 6 and Wi-Fi 7 edge	Class 4 to 6	802.3at or 802.3bt	Radio power changes	Class 4 or 6 ports
Outdoor PTZ and bridge links	Class 6 to 8	802.3bt Type 4	Heaters and long runs	Higher cable loss
Dual PSU core switch	Mixed classes	Redundant chassis	Failover capacity	Dual PSU derate

6PoE planning tips

Budget by class, then compare actual draw. Many switches reserve the full negotiated class or LLDP request, even when the connected device normally consumes less. Use the class allocation card for capacity approval and the expected draw line for thermal and PSU load planning.

Keep extra watts for startup and failover. Cameras enabling IR, APs changing radio power, and 802.3bt devices starting heaters can move together. A 10 to 20 percent reserve is usually a cleaner plan than filling every advertised watt.

This calculator estimates standard PoE class allocation. Vendor-specific perpetual PoE, passive PoE, nonstandard injectors, LLDP fine-grained negotiation, and cable bundle temperature limits may change the final switch configuration.

This is where you likely began: with a nice-looking switch, boasting sixteen ports, gigabit speed, and an ample-enough power budget to handle your small studio or home office. You hooked up the access points and cameras, ran some firmware updates… and now one of the devices has gone dark.

What’s the issue? Not the hardware. Math. Because power over ethernet is deceiving. It stay hidden until it reveals itself through browned-out devices.

Why You Need a Power Plan

In practice, defining your cable runs and device mix is all the heavy lifting the calculator above do for you, no more guesswork as to which IEEE class will apply to your particular setup.

And again: the problem is that switches reserve power according to what devices claim they might use versus what they’re using at any given second. A typical Wi-Fi access point may negotiate for up to thirty watts of PoE plus capacity to accommodate maximum radio transmission, though in reality it’s sipping only twelve watts most of the day. Those thirty watts are set aside by the switch out of the total pool, and never returned when the radio is powered down. This is where folks go wrong; they assume that power is dynamic when it’s reserved.

Now back to modeling a deployment: you’ll see from the IEEE tables that if you’re running cables around or near the hundred-meter mark, there’s significant voltage drop. This happens when you consider the difference between what the Powered Device gets and what the Power Sourcing Equipment need to send out, accounting for heat lost in the copper. For long runs, seven percent is a fair guess; it eats up some of your capacity even before power reaches the device. You aren’t just powering the signal at the end point; you are also paying for the watts that turn into heat in the walls.

Then there is the reserve margin. Fifteen percent of your budget seem like overkill; where do you go waste that? But startups surge. Multiple access points all reboot at once after a power glitch. Cameras turn on their infrared lights at dusk. The demand spikes and if your budget’s full, the switch shut down the lowest priority port to save itself. Small thing, sure, but when your security feed goes black, it matters.

There’s also the matter of redundancy. When you put in redundant power supplies to ensure failover, don’t consider them additive capacity. They still represent only one unit which is carrying the load, so you need to derate the total amount of available power by 50%. This is how the calculator works automaticly: showing you the actual usable headroom instead of the potential maximum. It removes all the marketing specs from the equation and presents you with the engineering reality.

Most of us treat PoE like a socket in a wall, but it is not. It’s a limited resource that needs coordination between peers. You can’t simply plug something into PoE and be done with it.

The presets in the tool are there because they’re common failure points. You can use a couple of Class 3 devices at home. It is a piece of cake. You might have a bunch of PTZ cameras with heaters and Wi-Fi 6 access points in a rack. That’s a whole other animal. Those higher-powered devices will pull too much power for your typical switch unless you assigns the right class to match.

Before even looking through the switch’s specs, there’s also reference table on the page which breaks down the classes and their respective power limits. If you know a particular device is a Class 8 device, drawing as much as ninety watts… That’s going to alter your rack planning. That could mean not forcing it into a general purpose switch, but rather using a dedicated high-power switch.

You don’t try and max it out. You build a system where nothing gets dropped in the worst case scenario. You want some reserve for when a bunch of devices all decide to reboot at once. You want a bit more so that next year adding another device isn’t a matter of replacing the entire chassis. Power planning is really about managing risk. You’re buying insurance against brown outs.

Write down your devices. Classify them. Plug ’em up. Do the math. Is the number tight? Downgrade your switch, or trim that reserve down. Dropping a camera at 3 AM sucks and upgrading a switch costs less than troubleshooting. You might ignore it, but the consequences isn’t. Those few extra watts can mean a stable network. You left ’em, so you own ’em.