PoE Power Budget Calculator
This free PoE calculator works out Power over Ethernet requirements for your network infrastructure. Get accurate power budgets, switch recommendations, and cable loss analysis based on IEEE 802.3 standards.
PoE Device Selection
Infrastructure Configuration
Ready to Calculate
Add your PoE devices to get power budget and switch recommendations
Common questions
How do I work out my PoE power budget?
Add the maximum draw of every powered device, then compare that against your switch’s total PoE budget — not its port count. A 24-port switch may only power a handful of 802.3bt devices. This calculator totals the draw, adds cable loss and shows the headroom left.
What is the difference between 802.3af, at and bt?
802.3af (PoE) delivers up to 15.4 W at the port, 802.3at (PoE+) up to 30 W, and 802.3bt (PoE++) up to 60 W (Type 3) or 100 W (Type 4). The device receives less than the port supplies because of cable loss.
How much power is lost in the cable?
Loss rises with length and falls with thicker copper. Over a full 100 m run, expect roughly 10-15% loss on Cat 5e and less on Cat 6/6a. The calculator applies this automatically from the cable type and length you choose.
Do I need to leave headroom on a PoE switch?
Yes. Running a PoE budget at 100% leaves nothing for future devices and no margin if a device draws its peak. Plan to a percentage of the switch budget and add an expansion allowance — both are inputs here.
Planning the wireless side too? use the free WiFi calculator to size access points, or design the whole floor plan in WiFi Weave.
Important Disclaimer
For Educational and Estimation Purposes Only: The PoE Power Budget Calculator is provided as a free educational tool to help with preliminary planning estimates. Results should not be used as the sole basis for professional network deployments.
Professional Consultation Required: For production networks, always consult qualified professionals and conduct proper site surveys. Actual results may vary significantly based on environmental factors, building materials, interference, and specific requirements.
Methodology: Results are based on industry-standard guidance and the sources referenced below, simplified for general use. Real-world deployments require detailed analysis of specific conditions.
- Power consumption values are based on typical device specifications and may vary by manufacturer
- Cable resistance and temperature can significantly affect power delivery
- Environmental factors and cable quality impact actual power requirements
- Consider voltage drop calculations for longer cable runs
- Power redundancy planning is essential for mission-critical deployments
Sources & References:
- IEEE 802.3af-2003 - Power over Ethernet Standard
- IEEE 802.3at-2009 - Power over Ethernet Plus Standard
- IEEE 802.3bt-2018 - Power over Ethernet Plus Plus Standard
- TIA-568 Commercial Building Telecommunications Cabling Standard
- Industry best practices for PoE deployment and power budgeting
Limitation of Liability: WiFi Weave makes no warranties regarding the accuracy or completeness of these calculations. Users assume all responsibility for decisions based on these estimates.