Power over Ethernet (PoE / PoE+ / PoE++) Switch Budget & Cable Loss Calculator

Size PoE switches accounting for Cat6 cable heat loss and 20% headroom.

Recommended Switch PoE Power Budget
365.82 W
PSE Output Required per Port 19.05 W/port
Cable Resistance Loss per Port 1.05 W/port
Net PD Load Without Headroom 304.85 W
Inputs
devices
Number of PoE powered devices (APs, IP cameras, phones).
W/device
Power draw at each Powered Device (PD) in Watts.
m
Average Ethernet cable run length in meters (max 100 m).
Ω/100m
DC loop resistance per 100 m (12.5 Ω Cat6, 18.8 Ω Cat5e).
Results & Graph
Recommended Switch PoE Power Budget
365.82 W
PSE Output Required per Port
19.05 W/port
Cable Resistance Loss per Port
1.05 W/port
Net PD Load Without Headroom
304.85 W

Recommended Switch PoE Power Budget

Graph 1 • Powered Devices Count Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
0 W 296.3 W 592.6 W 50%: 182.91 W 182.9 50% 75%: 274.36 W 274.4 75% 100%: 365.82 W 365.8 100% 125%: 457.27 W 457.3 125% 150%: 548.73 W 548.7 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Recommended Switch PoE Power Budget 365.82 W PSE Output Required per Port 19.05 W/port Cable Resistance Loss per Port 1.05 W/port Net PD Load Without Headroom 304.85 W
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Recommended Switch PoE Power Budget365.82 WPSE Output Required per Port19.05 W/portCable Resistance Loss per Port1.05 W/portNet PD Load Without Headroom304.85 W
Summary: 16 devices drawing 18 W each over 65 m dissipate 1.05 W/port in cable resistance (19.05 W at PSE); with 20% headroom, size a 366 W PoE switch.
Summary: 16 devices drawing 18 W each over 65 m dissipate 1.05 W/port in cable resistance (19.05 W at PSE); with 20% headroom, size a 366 W PoE switch.
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Interactive chart & math engine powered by CalculatorGraph

Formula & Mathematical Methodology: PoE Switch Power Budget Systems Engineering Formula

PortPSEWatts = PDLoadWatts / (1 − CableLossRatio)
SwitchBudget = Devices × PortPSEWatts × 1.20
PortPSE_Watts = PD_LoadWatts / (1 − CableLossRatio); SwitchBudget = Devices × PortPSE_Watts × 1.20
  • poweredDevicesCount: Powered Devices Count (devices)
  • wattsPerDevicePd: Watts Per Device Pd (W/device)
  • cableLengthMeters: Cable Length Meters (m)
  • loopResistanceOhmsPer100m: Loop Resistance Ohms Per100m (Ω/100m)

Rounding: Binary/decimal capacities and engineering metrics retain full floating-point precision and round to 2 decimal places.

Worked Example: Architecture Sizing Example: PoE Switch Power Budget

Size PoE switches accounting for Cat6 cable heat loss and 20% headroom.

  1. Enter the workload parameters, model dimensions, or network link specifications.
  2. Compute the sizing equation: PortPSE_Watts = PD_LoadWatts / (1 − CableLossRatio); SwitchBudget = Devices × PortPSE_Watts × 1.20.
  3. Inspect the primary capacity metric, headroom buffers, and 3 SVG visualizations.
Result: Calculates PoE Switch Power Budget via PortPSE_Watts = PD_LoadWatts / (1 − CableLossRatio); SwitchBudget = Devices × PortPSE_Watts × 1.20.

Frequently Asked Questions

How does the Power over Ethernet (PoE / PoE+ / PoE++) Switch Budget & Cable Loss Calculator compute capacity?

It evaluates PortPSE_Watts = PD_LoadWatts / (1 − CableLossRatio); SwitchBudget = Devices × PortPSE_Watts × 1.20 directly in your browser and plots three custom SVG diagrams.

Can I compare different cluster or model configurations side by side?

Yes. Use the "Compare (0/3)" button in the results panel to pin up to three configurations.

Does this tool upload any of my architecture parameters?

No. All calculations run 100% client-side in your browser.

Developer Tools · Networking & Digital Systems

Power over Ethernet (PoE / PoE+ / PoE++) Switch Budget & Cable Loss Calculator: inputs, method, and how to read the result

Size PoE switches accounting for Cat6 cable heat loss and 20% headroom.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Powered Devices Count: Number of PoE powered devices (APs, IP cameras, phones).
  • Watts Per Device Pd: Power draw at each Powered Device (PD) in Watts.
  • Cable Length Meters: Average Ethernet cable run length in meters (max 100 m).
  • Loop Resistance Ohms Per100m: DC loop resistance per 100 m (12.5 Ω Cat6, 18.8 Ω Cat5e).

What the calculation includes

With the default values shown, Recommended Switch PoE Power Budget is 365.82 W. The calculation follows PoE Switch Power Budget Systems Engineering Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Powered Devices Count from 16 devices to 18 devices changes Recommended Switch PoE Power Budget from 365.82 W to 411.54 W. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses industry-standard IEEE, IETF RFC, and GPU/cloud hardware sizing conventions.
  • Capacity planning estimate; benchmark under production traffic patterns before finalizing cluster or hardware procurement.

Scope: IEEE / IETF / Cloud Systems Engineering Standard Check the assumptions and limitations against your situation before relying on the estimate.

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