PoE Budget Calculator
Check an approximate PoE watt budget before expanding cameras, access points, phones or other powered devices.
How to use this calculator
- Enter the switch poe power budget (w) using the units shown beside the field.
- Enter the power reserve (%) using the units shown beside the field.
- Enter the devices planned using the units shown beside the field.
- Review the calculated values and check that the assumptions match your scenario.
- Change one input at a time when comparing scenarios so you can see which assumption drives the result.
Formula and assumptions
Usable budget = switch budget × (1 − reserve); device load = count × watts per device; supported count = floor(usable budget / per-device watts).
- Use the switch’s actual PoE standard, per-port limit, power-sharing rules and startup draw. This estimate does not replace hardware specifications.
- The result is computed from the values you provide; it does not fetch external rates, live account data or local rules.
Worked examples
Worked example
A 370 W budget with 20% reserve leaves 296 W. Devices drawing up to 13.5 W each allow 21 devices by the simplified budget calculation.
Example inputs: Switch PoE power budget (W) = 370, Power reserve (%) = 20, Devices planned = 18, Maximum power per device (W) = 13.5.
Compare the displayed output with your own measurements before using it in a decision.
Understanding the result
Use the switch’s actual PoE standard, per-port limit, power-sharing rules and startup draw. This estimate does not replace hardware specifications.
Results are estimates based on the stated model. If the situation depends on measured conditions or contractual specifications, use those source values rather than typical assumptions.
Important notes
Use the switch’s actual PoE standard, per-port limit, power-sharing rules and startup draw. This estimate does not replace hardware specifications.
Frequently asked questions
What formula does this calculator use?
It uses the method described above: Usable budget = switch budget × (1 − reserve); device load = count × watts per device; supported count = floor(usable budget / per-device watts).
What should I verify before relying on the result?
Use the switch’s actual PoE standard, per-port limit, power-sharing rules and startup draw. This estimate does not replace hardware specifications.
Can I compare different scenarios?
Yes. Change the inputs while keeping units and definitions consistent, and record the assumptions used for each scenario.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.