Power over Ethernet
PoE budget calculator
Add your access points and cameras, then check whether the switch has enough total power and sensible safety headroom.
Your inputs
Calculated result
95 W requested
The devices may draw up to 95 W from a 120 W budget, leaving 25 W headroom.
Switch budget
120 W
Headroom
25 W
Headroom percent
21%
How to use this result
- • Use maximum device power, not typical draw, for conservative planning.
- • Keep roughly 20% headroom for startup peaks, environmental variation, and future devices.
- • Total wattage does not replace checking the PoE standard required by each port.
How the calculation works
- Multiply each device type's count by its maximum PoE power draw from the manufacturer data sheet.
- Add the totals to get the worst-case power the devices can request.
- Compare that total with the switch's total PoE budget: more than the budget is incompatible.
- If less than 20% of the budget remains as headroom, the result is a warning rather than a pass.
Worked example
3 Wi-Fi 7 access points and 4 cameras on a 120 W switch
- 3 access points × 21 W = 63 W
- 4 cameras × 8 W = 32 W
- Total requested: 95 W of a 120 W budget
The devices may draw up to 95 W from a 120 W budget, leaving 25 W headroom. That is 21% of the budget, above the 20% warning threshold, so the switch passes.
Common questions
Should I use typical or maximum power draw?
Use maximum draw. Devices peak during boot, radio activity, camera IR at night, or heater operation outdoors, and the switch must supply that peak without cutting power to a port.
What do PoE, PoE+ and PoE++ provide per port?
IEEE 802.3af (PoE) supplies up to 15.4 W at the switch port (12.95 W at the device), 802.3at (PoE+) up to 30 W (25.5 W at the device), and 802.3bt (PoE++) up to 60 W (Type 3) or 90 W (Type 4) at the switch port.
Is a big enough total budget sufficient?
No. Each port must also support the PoE standard the device requires, and the switch needs enough PoE-capable ports. A device needing PoE+ will not work reliably on an 802.3af-only port even if the total budget is large.