Calculator · CCTV · IEEE 802.3
PoE budget calculator
Enter the switch's total PoE budget, then the devices on it in up to four groups: how many, and the watts one draws from its data sheet. You see the total, how much of the budget is left, and any device that draws more than the port type can give.
Result
Enter the switch budget and at least one group of devices to see the result.
Working
total device watts ≤ switch budget × (1 − headroom)
- Total = the sum of (number of devices × watts each) for every group.
- Usable budget = the switch budget × (1 − headroom). Headroom covers cable loss, start-up surges and later additions.
- Power at the port and at the device: 802.3af (Type 1) 15.4 W and 12.95 W; 802.3at (Type 2) 30 W and 25.5 W; 802.3bt Type 3 60 W and 51 W; 802.3bt Type 4 90 W and 71.3 W.
- Ethernet cable runs are limited to 100 m.
Source: IEEE 802.3af, 802.3at and 802.3bt, as set out by the Ethernet Alliance and chip makers. Some sources round the lowest class to 13 W at the device. The headroom figure is your own choice. There is no fixed figure in the standard.
Check the switch's data sheet for how it shares its budget across ports. Some switches have a per-port limit as well as a total.
For guidance only. Always check against the current edition of the standard and the manufacturer's data.
Built by the engineer behind Kerova, certificate software for fire and security firms.