PoE Budget Calculator for IP Cameras
Size your PoE switch, pick the right 802.3 class, and check cable-run voltage drop in one screen. Free — no signup.
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Typical: 5–8 W fixed dome, 8–12 W IR bullet, 12–25 W vandal IR or mini-PTZ, 25–50 W full PTZ, 50–70 W heated PTZ or multi-sensor.
IEEE PoE spec guarantees 100 m on Cat5e. Past that you need Cat6, an extender, or a mid-span injector.
Recommended switch + class
Recommended PoE class per port
802.3af (PoE)
Up to 15.4 W source-side, guarantees 12.95 W at the camera over 100 m Cat5e.
Switch power budget (with 20% headroom)
348 W
17 ports needed. Devices draw 168 W at the PD; source side is 290 W before headroom.
Estimated voltage drop on longest run
2.01 V → 46.0 V at PD
Cable run is within IEEE spec for the recommended class.
IEEE 802.3 PoE class reference
| Class | Source W | At PD | Typical use |
|---|---|---|---|
| 802.3af (PoE) | 15.4 W | 12.95 W | Fixed-lens domes, simple bullets |
| 802.3at (PoE+) | 30 W | 25.5 W | IR bullets, vandal domes, mini-PTZ |
| 802.3bt T3 (PoE++) | 60 W | 51 W | Full PTZ, IR illuminators |
| 802.3bt T4 (Hi-PoE) | 90 W | 71.3 W | Heated PTZ, multi-sensor 360°, ALPR |
FAQ
What is PoE and which class should I use for IP cameras?
PoE (Power over Ethernet, IEEE 802.3af / at / bt) delivers DC power and data over the same Cat5e/Cat6 cable. Pick 802.3af (15.4 W) for fixed lens cameras drawing under 13 W at the PD, 802.3at / PoE+ (30 W) for dome/bullet cameras with strong IR or pan-tilt, 802.3bt Type 3 (60 W) for PTZ and heaters, and Type 4 (90 W) for multi-sensor 360° cameras with heated housings.
How big should my PoE switch's power budget be?
Sum the source-side wattage of every powered device (each camera's PoE class × count, plus any PoE NVR), then add at least 20 % headroom for startup spikes and future expansion. A 16-camera 802.3at install needs about 16 × 30 = 480 W of port capacity plus ~96 W headroom — roughly a 600 W switch budget. Always check the switch spec sheet for 'total PoE power budget', not just per-port maximum.
How much voltage drop is acceptable on a long PoE run?
IEEE allows about 6 V of drop across 100 m of Cat5e. Beyond that, the PD won't reliably negotiate. This calculator estimates drop using 12.5 Ω loop resistance per 100 m (Cat5e 24 AWG, 2-pair for af/at, 4-pair for bt). For runs over 100 m, use Cat6 (lower resistance), upgrade to 802.3bt 4-pair, or add a PoE extender / mid-span injector.
Can I use a PoE injector instead of a managed PoE switch?
Yes for one to three cameras — a single-port PoE+ injector is cheaper than a managed switch and works for small home installs. For 4+ cameras or any commercial install, a managed PoE switch is mandatory: it consolidates the power budget, supports VLANs (separate camera traffic from data), enables per-port PoE control for remote reboots, and exposes link/PoE-class monitoring via SNMP for ongoing maintenance.
What's the difference between PoE 'budget' and 'per-port maximum'?
Per-port maximum is the upper bound a single port can deliver (e.g. 30 W on a PoE+ port). The total budget is the sum the switch's power supply can deliver across ALL ports simultaneously. An 8-port PoE+ switch might advertise '30 W per port' but only 120 W total — so you can power 4 cameras at 30 W, not 8. Always check the 'PoE Power Budget' line in the spec sheet.
Do PoE cameras work with non-PoE Ethernet ports?
No. A PoE-only camera (no 12 V DC input) requires a PoE source — either a PoE switch or a PoE injector inline before a regular switch. Dual-input cameras (PoE + 12 V DC) can take either, useful in retrofit installs where the existing switch is non-PoE. Always confirm 'PoE or 12 V DC' on the camera datasheet before designing the run.
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