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Network Engineer

PoE Power Budget Calculator

Use this poe power budget calculator entirely in your browser.

ResultPoE budget required: 205.333333333 W

Entered switch budget: 250 W (sufficient).

Remaining margin: 44.6666666667 W.

Calculations happen locally in your browser.

How to use this calculator

  1. Enter the labelled values and review the live result.
  2. Review the live result and use Copy result when you need to share it.

How the calculation works

Device count multiplied by maximum device watts is increased by the entered cable and planning allowance.

Formula

Device count multiplied by maximum device watts is increased by the entered cable and planning allowance.

Step-by-step calculation

  1. Enter the labelled values and review the live result.
  2. Device count multiplied by maximum device watts is increased by the entered cable and planning allowance.
  3. Check the displayed result, then copy it if needed.

Worked example

Twelve 15.4 W devices with a 10% loss allowance require about 205.3 W.

Methodology and review

Who this is for

Installers sizing a switch power budget.

Inputs and units

  • Device count
  • Watts per device
  • Switch budget
  • Reserve

Method

Per-device power is multiplied by device count and compared with switch budget after the selected reserve is retained.

Worked example

Eight 12 W devices require 96 W before reserve.

Assumptions

  • Entered watts represent realistic maximum device draw.
  • Every powered port shares the stated switch budget.

Common mistakes

  • Using average rather than maximum draw
  • Ignoring cable and temperature allowances

Limitations

  • Cable loss, class negotiation, temperature derating, redundant supplies, and startup peaks require vendor checks.
  • The tool does not certify standards compliance.

How this tool was checked

Tests verify aggregate load, reserve, remaining capacity, and over-budget states.

Related tools

Calculation review: 21 August 2026. Published by Goldwave Dynamics Limited. This is an internal product review, not an independent certification.

Risk guidance

Frequently asked questions

Does this tool send my inputs anywhere?

No. The interactive calculation runs in your browser and this site does not submit tool inputs to a backend.

How should I use the result?

Check that the entered units and values match your situation, especially around dates, breaks, and rounding.

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