Network PoE Budget Calculator

A switch's total PoE power budget (for example 740W on a typical 48-port PoE+ switch) is a hard ceiling set by its power supply, and it's almost always far less than what every port could draw if fully loaded simultaneously. The calculator multiplies switch count by each switch's rated PoE budget rather than port count times per-port maximum, because port count alone would badly overstate how much power the switches can actually deliver.

It looks at the single highest-wattage device across all your categories (phones, APs, cameras, other) rather than the total load, since the PoE standard is a per-port capability, not an aggregate one. Anything under 15.4W fits basic IEEE 802.3af (2003), above that up to 30W needs IEEE 802.3at (PoE+, 2009), and devices like PTZ cameras or high-power APs pushing past 30W or 60W require IEEE 802.3bt Type 3 or Type 4 (2018) -- a switch with plenty of total budget can still fail to power one demanding device if its per-port standard is too low.

The calculator assumes every device draws exactly its rated wattage simultaneously, which is usually conservative since actual draw fluctuates with device state. But PTZ camera motors and high-power APs under full load can spike above their nameplate rating, so running your utilization right up to 100% of budget leaves no headroom for those real-world spikes -- keeping utilization comfortably below 100% avoids devices browning out during peak draw.

These take whatever budget remains after your current device load and divide it by a single device's wattage (per-phone or per-AP) to estimate how much more of that device type the existing switch budget could support. It's a quick growth-planning check -- for example, confirming you can add another floor of IP phones without buying a new switch -- rather than a full re-spec that accounts for adding multiple device types at once.