PoE Budget Calculator
Will these cameras, access points and phones fit on this PoE switch?
Try before you buy.
- Free preview: the power budget left and the verdict, with the first rows of the device and room-for-more tables; the totals, ports and other figures are hidden.
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Result
Device by device
Room for more devices
Power classes: IEEE 802.3 Clause 33 (Type 1 and 2) and Clause 145 (Type 3 and 4), from the IEEE GET Program. Estimates only: the switch’s and the devices’ datasheets decide.
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Results are estimates from the formulas shown, not a professional design or certification. Have a qualified engineer verify anything safety-critical (structures, electrical installations, gas or pressure systems).
About the PoE Budget Calculator
A PoE switch has two limits: the power each port can deliver, set by its PoE type, and the total budget of the whole switch, which is usually far less than every port at full power. List the devices you want to power — cameras, Wi-Fi access points, phones, anything with a PoE class — and the calculator checks both, the way switches count: by class (each port reserves its class maximum) or by draw (what the device asks for or uses, plus the loss in the cable).
It uses the IEEE 802.3 classes: what the switch port (PSE) must deliver and what the device (PD) may draw at the end of up to 100 m of cable — 15.4 and 12.95 W for Class 3 (802.3af), 30 and 25.5 W for Class 4 (802.3at), 60 and 51 W for Class 6 and 90 and 71.3 W for Class 8 (802.3bt). You get the power left, the share of the budget used, the ports used, each device’s figures and problems (a Class 6 camera on a PoE+ port, a draw above its class) and how many more devices of each class would fit.
Without a pass, the free preview shows the power left and the verdict in full, with the first rows of the device and room-for-more tables; the totals, the ports, the other figures, the copied summary and the CSV unlock with a Pro pass.
How to use it
- Enter the switch’s PoE budget in watts and its PoE ports with their type, from its datasheet. Open Ports of a second type if it has, say, a few 90 W ports and many 30 W ones.
- Choose how the switch counts devices: by class (the safe assumption) or by draw (if it allocates by LLDP or measured power).
- List the devices: a name, how many, the PoE class from the device’s datasheet or label and, if you know it, its maximum draw in watts.
- Read the power left and the checks; fix any device that needs a better port type. With a pass, copy the summary or download the table as CSV (in the free preview they stay locked).
Examples
6 Wi-Fi access points (Class 4) · 10 IP cameras (Class 3) · 4 desk phones (Class 2)
6 × 30 W + 10 × 15.4 W + 4 × 7 W = 362 W → 8 W left, 20 of 24 ports used
Access points draw 21 W, cameras 9 W, phones up to their class maximum
6 × (21 + 4.5) + 10 × (9 + 2.45) + 4 × 7 = 295.5 W → 74.5 W left
Each draw counts with its class’s worst-case cable loss: the difference between the port’s and the device’s power.
Not enough ports of the right type: it needs a Type 3 (802.3bt) port or better
Common uses
- Check that a new PoE switch can power every camera of a CCTV system, heaters and infrared at full power included.
- Plan the Wi-Fi access points of an office floor against the budget of the switch in its comms cupboard.
- Find out how many more phones or cameras an existing switch can take.
- Choose between a PoE+ and an 802.3bt switch for PTZ cameras, displays or access points that need more than 30 W.
IEEE 802.3 power classes
Power at the switch port (PSE) and at the device (PD) for each class:
- Class 0 (Type 1): 15.4 W at the port, 12.95 W at the device
- Class 1 (Type 1): 4 W and 3.84 W
- Class 2 (Type 1): 7 W and 6.49 W
- Class 3 (Type 1): 15.4 W and 12.95 W
- Class 4 (Type 2): 30 W and 25.5 W
- Class 5 (Type 3): 45 W and 40 W
- Class 6 (Type 3): 60 W and 51 W
- Class 7 (Type 4): 75 W and 62 W
- Class 8 (Type 4): 90 W and 71.3 W
Type 1 is the old 802.3af (“PoE”), Type 2 802.3at (“PoE+”), Types 3 and 4 802.3bt (often sold as “PoE++”). A port of a type powers its own classes and every lower one. The difference between the two columns is the most the cable may lose over 100 m at that class. Class 0 is a device that does not state its class; the port treats it as up to 15.4 W.
Sources: IEEE 802.3, Clause 33 (Type 1 and 2) and Clause 145 (Type 3 and 4, from IEEE 802.3bt), through the IEEE GET Program; the IEEE 802.3bt task force.
By class or by draw?
A switch that allocates by class reserves the class maximum at the port as soon as a device is detected — 30 W for every Class 4 access point, even one that draws 12 W. That is the safe figure to plan with. Switches that allocate by LLDP or measured power reserve only what the device asks for or uses, so more devices fit; the calculator then counts each device’s datasheet maximum plus its class’s worst-case cable loss. Your switch’s manual says which it does, and many let you choose per port.
Plan with the datasheet’s maximum draw, not the typical one: a camera’s heater or infrared lights, or an access point at full load, can draw much more than it does at idle. Keep a reserve for devices you will add later.
Limitations
- Estimates only, not an electrical design: the switch’s and the devices’ datasheets decide, and some switches reserve power their own way.
- Cable loss is taken as the worst case of each class (100 m); shorter cables lose less.
- Pre-standard and vendor-specific PoE (passive 24 V, 60 W schemes before 802.3bt) and dual-signature devices are not modelled.
- The total budget of some switches depends on their power supplies, or is lower at high temperatures; use the figure for your configuration.
Privacy
On this device: nothing is sent
Everything is calculated in your browser. The devices you list are not uploaded or stored.
Frequently asked questions
What do I get without a pass?
Without a pass, PoE Budget Calculator shows the power budget left and the verdict, with the first rows of the device and room-for-more tables; the totals, ports and other figures are hidden. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
How much power does each PoE class use?
At the switch port: Class 1 4 W, Class 2 7 W, Class 0 and 3 15.4 W, Class 4 30 W, Class 5 45 W, Class 6 60 W, Class 7 75 W, Class 8 90 W. At the device a little less: 3.84, 6.49, 12.95, 25.5, 40, 51, 62 and 71.3 W.
What is the difference between PoE, PoE+ and PoE++?
They are the common names of the IEEE types: PoE is 802.3af (Type 1, up to 15.4 W per port), PoE+ is 802.3at (Type 2, 30 W) and PoE++ is 802.3bt (Type 3, 60 W, and Type 4, 90 W, over all four pairs).
Why is the power at the device lower than at the switch?
Part of the power is lost as heat in the cable. The standard sets the port’s output so that the device still gets its class power at the end of 100 m of cable: 30 W at the port gives at least 25.5 W at a Class 4 device.
Can a PoE+ switch power an 802.3bt device?
Not at its full class. A Class 5–8 device needs a Type 3 or Type 4 port; on a PoE+ port it either does not start or runs in a reduced mode if its maker allows it. Check the device’s datasheet.
How do I find a device’s PoE class?
In its datasheet or on its label, often next to the power consumption (“PoE Class 4” or “802.3at”). The switch also shows the class it detected for each port.