Power over Ethernet calculator ( PoE ) to find Line Loss
Maximum PoE Distance, PoE voltage drop and resistance

PoE Tester

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This PoE calculator by PoE-World will calculate the total power required for any device including cable loss by any type or length of cable, over Ethernet or not, it calculates the voltage drop and power required by both the device and the loss in the cable.

A Number of pairs used for POE
1 simple wire
2 Passive 2 pair
2 802.3af, 802.3at, PoE+
4 802.3bt, UPoE 4 pair

BCable type
Cat-5e Copper
Cat-6 Copper
Cat-6a Copper
Cat-7 Copper
Cat-5e low cost Cu/Al
Cat-6 low cost Cu/Al
Cat-5e cheap

Or enter
your own
Ohms/1000 ft

see AWG table below
C (ft)Distance in ft
---(328 is max for Ethernet)--- ft or
C (m) Distance in Meters
---(100 is max for Ethernet)--- mtr
DSupply Voltage (56v max)
802.3at 56 Volts
802.3at 51 Volts
802.3af 48 Volts
UBNT/MT 24 Volts
Thin Client 19.5 Volts
non-PoE 12 volts
non-PoE 5 volts
USB 5 Volts

or other
E (a) Amps required ( or )
Amps or
E (w) Watts required remotely
FNumber of Devices to power

  • Cat-5e and Cat-6 cable is sold in pure Copper and in Copper / Aluminum alloy ( Cu/AL ) variations.
  • Cu/Al is standard at Home Depot etc, and unless specified, assume all CAT-5 isn't copper
  • Cu/Al has higher resistance, so the loss is greater.
  • There is also extremely low cost cable that uses thinner 28 AWG wire on the 45 and 78 pairs, resulting in high loss.

Since a device is spec'd for power consumption over a range of input voltages, as the remotely delivered voltage decreases with distance, the amps increase, causing the delivered voltage to decrease further.

See our list of popular PoE devices for voltage specs here

This Voltage Drop Calculator can be used for any type of wire and gauge. Unlike other calculators - you can enter the power required by the device in order to calculate total power including the effects of voltage drop and line loss. It will calculate and display the max cable distance, and is easier to use than a basic voltage drop tool.

Our Calculator will give a warning if the link is too long
At long distances, the result is unstable and cannot be solved
we will suggest minimum voltages for the length entered

If you have more than one device per endpoint
change the value in line F

Chinese CCA cat-5 uses 28 awg on the power pairs @ 101 ohms

one CAT-5e spec

Ohms per 100 ft at different temperatures