Free tool · UK
PoE & voltage drop calculator
Find out if a camera will work at the end of its cable before you run it. On PoE, we check the run is no longer than 100m and that the camera gets enough power. On 12V, we work out how much voltage the cable loses. If the run won’t work, you’ll see what to change.
This run will work
- Your 30m run is inside the 100m limit for network cable.
- A 6W camera is within the 12.95W a camera gets on 802.3af (PoE), with 6.9W to spare.
- Check the switch’s total budget too. Plenty of 8-port switches can’t run eight cameras flat out on every port at the same time.
Our PoE switches
See all networking- 4 port4 Port Gigabit POE Extender 1000M Network Switch Repeater IEEE802.3af/at Plug&Play for PoE Switch NVR IP Camera AP£14.85
- 8 portHikvision DS-3E0510P-E 8-Port Gigabit PoE Unmanaged Network Switch£79.90
- 9 portHikvision DS-3E0109P-E/M 9-Port PoE Switch 8×PoE 100Mbps Long Range 300m£57.44
- 16 portHikvision DS-3E0518P-E 16-Port Gigabit PoE Unmanaged Network Switch£203.55
- 24 portHikvision DS-3E0326P-E/M(B) 24-Port PoE Unmanaged Network Switch£205.85
Ports are the easy part. Add up what your cameras draw and compare it with the switch’s total PoE budget, not the figure for one port. The total is what runs out first.
The simple rules behind it
PoE works up to 100m over Cat5e or Cat6. How much power reaches the camera depends on the PoE standard: 802.3af gives a camera 12.95W, 802.3at gives it 25.5W, and 802.3bt gives it 51W. One camera is rarely the problem — the switch is. Add up what all your cameras draw and compare it with the switch’s total PoE budget, not just what one port can give.
On 12V, the cable itself is the problem. Copper loses voltage along the way, and the current has to travel out to the camera and back again. Double the run and you double the loss; go up a cable size and you halve it. Most cameras cope with about 10% less than 12V (10.8V). But the infrared comes on at night and can double what a camera draws, so a run that’s fine at 3pm can cut out at midnight. If a run fails, use thicker cable, move the power supply nearer the camera, use 24V equipment, or switch that camera to PoE.