PoE power budget calculator
Is your switch's PoE budget enough for these devices? Enter the total budget and the device list (class or W, quantity); see the allocation, remaining budget, utilization, safety margin and port count. If you enter device-side consumption and a cable loss share, an estimate of real consumption is added.
Results
- Total allocation
- 630.4 W
- 28 devices; allocation by class or the W you wrote
- Budget utilization
- 85.2 %
- 630.4 W / 740 W total budget
- Usable budget
- 666 W
- 740 W − 10% safety margin (74 W)
- Remaining budget
- 35.6 W
- Within the usable budget
- Real consumption estimate
- 357.9 W
- No device-side value was entered for 2 devices; they were counted at their allocation
- Remaining against real consumption
- 308.1 W
- Within the usable budget
- Devices that can be powered in list order
- 28 / 28
- All listed devices fit in the usable budget
- Additional devices with the remaining budget
- af: 2 · at: 1 · bt type 3: 0 · bt type 4: 0
- Ports
- 28 / 48
- 20 free ports
Device breakdown
| Device | Qty | Class | Allocation (W) | Device side (W) | Total allocation (W) |
|---|---|---|---|---|---|
| Wi-Fi access point | 8 | at (typical) | 30 | 18 | 240 |
| IP camera | 10 | af (typical) | 15.4 | 7 | 154 |
| PTZ camera | 2 | bt3 (typical) | 60 | 40 | 120 |
| IP phone | 6 | af (typical) | 15.4 | 4 | 92.4 |
| Door controller | 2 | entered W | 12 | — | 24 |
Calculation and assumptions
- Allocation (W) = Σ device allocation × qty; device allocation = the class's typical PSE output or the W you wrote. Usable budget = total budget × (1 − safety margin %).
- Real consumption estimate = Σ device-side W × (1 + cable loss %) × qty. Devices without a device-side value are counted at their allocation; if none has one, this result is not shown.
- Remaining budget = usable budget − allocation. Utilization % = allocation / total budget. If the allocation exceeds the usable budget it eats into the safety margin; if it exceeds the total budget, the budget is exceeded.
- Devices that can be powered in list order: devices are added in sequence until the usable budget is full. Additional devices = ⌊remaining budget / class PSE power⌋. Port check: total device count ≤ number of PoE ports.
The values you enter are processed in your browser; they are not sent to a server and not stored.
This is a preliminary check. Switches may manage power by static class allocation, by LLDP or by measured power; which mode applies and the per-port limits are in the switch documentation. The typical PSE values are editable as in the table and must be verified against documentation; a device's real consumption is mostly below its allocation, but transient loads (heated cameras, PTZ movement) may approach it.
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How to use
A
Enter the switch's total PoE budget, a safety margin and (optionally) the number of PoE ports; if needed edit the typical PSE output powers in the table to match your documents.
B
Write the devices as name;class or W;quantity; if you know the device-side consumption, add it in the fourth field.
C
See the allocation, remaining budget, utilization, overrun warning, real consumption estimate and how many additional devices fit; copy the result.
02
The difference between allocation and real consumption
When a device is connected to a port, the switch usually reserves (allocates) power according to the device's class; this may be higher than what the device really draws. If the total allocation exceeds the switch's PoE budget, the last connected or non-priority ports may not get power. That is why the tool compares the allocation with the budget first.
If you enter device-side consumption (from the device documentation or a measurement), a real consumption estimate is also calculated by adding the cable loss share. If the switch manages power by measured draw this value is more meaningful; if it uses static allocation by class, the allocation is what counts.
03
Classes and typical powers
The typical PSE output is quoted as about 15.4 W for IEEE 802.3af type 1, 30 W for 802.3at type 2, 60 W for 802.3bt type 3 and 90 W for type 4. A device need not draw all of this; the PSE output is the power reserved on the switch side, including losses in the cable. Verify the values against the switch and device documentation; that is why the table in the tool is editable.
In the list you can write W directly instead of a class, for example for a device whose documentation gives a specific power value. Devices of the bt classes (PTZ cameras, displays, heated access points) use up the budget quickly.
04
Safety margin and growth
Leaving a share of the budget unused instead of using all of it covers adding new devices, a heater running in cold weather, or measurement uncertainty. The tool gives separate warnings when the allocation eats into the safety margin and when it exceeds the total budget.
It also shows how many additional devices of each class fit in the remaining budget. The port count can be a limit too: even if the budget suffices, a device cannot be connected without a port; hence the optional port check.
FAQ
- Is my input sent anywhere?
- No. The calculation runs in code in your browser; values are not sent to any server and are not stored.
- Where do I find the total PoE budget?
- It is in the switch model's datasheet or management interface. The same model can have different budgets depending on the power supply option; enter the value for your own installation.
- Why is the PSE power in the table editable?
- These values are typical output powers; some switches or devices may reserve different values. You can change them to match your documentation.
- Why do device-side consumption and allocation differ?
- The allocation is the power the switch reserves from the port by class; the device often draws less. There is also a loss in the cable; this is why the real consumption estimate adds a cable loss share to the device-side value.
- What if the allocation exceeds the budget but real consumption fits?
- If the switch manages by measurement the devices may work; if it uses static allocation by class, the last connected ports may not get power. Verify which applies in the switch documentation; for critical devices it is safer to plan by allocation.
- How big should the safety margin be?
- That depends on your operating conditions: devices to be added, ambient temperature and measurement uncertainty. The tool suggests no particular value; you can try different margins and watch the result.
Is your PoE budget at the limit?
Let us plan the switch, PoE, cabling and camera/access point layout together, and set up budget, redundancy and monitoring correctly from the start. In a free discovery call we discuss your current state.