TechFuel HQHow to use this calculator
Enter how many of each PoE device you have — access points, fixed cameras, PTZ cameras, VoIP phones, and anything else — with the wattage each draws. Set the average cable run length and a headroom percentage, and the calculator returns the total switch PoE budget you should buy. Enter your switch’s actual budget too, and it tells you whether it fits with watts to spare or falls short.
The defaults are typical values; for an accurate result, set each device’s real rated draw (it’s on the spec sheet or the device itself).
Switch budget vs. device draw
A PoE switch advertises a total PoE budget — say 60 W or 250 W — which is the combined wattage it can deliver across all ports at once, measured at the switch (the PSE, power-sourcing equipment). Your devices (PDs, powered devices) are rated by what they consume, and the difference between the two is lost in the cable. So the budget you need isn’t just the sum of device labels: it’s that sum, plus cable losses, plus headroom. Size for the switch side, not the device side.
The headroom rule
Always leave room. Power-on inrush, an AP that ramps up under a full client load, a camera switching on night-vision IR, and underestimated cable loss all push real draw above the nameplate sum. About 20% headroom keeps ports reliable and leaves space to add a device later. A switch run at 100% of budget will start dropping power to ports the moment something spikes — usually as a confusing, intermittent outage rather than a clean failure.
What this pairs with
Once you know the budget, the budget homelab networking gear guide covers switches that hit common budget tiers, and the MikroTik CRS305 review is worth a look if you’re combining PoE with a 10GbE uplink. If your APs are the big draw, the Wi-Fi 7 guide covers which APs need PoE+/bt versus plain PoE.