– CONDUCTOR CALCULATOR · TSG LABS TOOLS

Conductor and Voltage-Drop Calculator

Sizes copper or aluminum conductors for low-voltage security and door-hardware circuits. Source voltage, current draw, one-way distance, and a voltage drop budget go in. Recommended AWG, actual drop in volts and percent, voltage at load, and an ampacity check come out. Useful for mag locks, electric strikes, REX devices, card readers, IP cameras (non-PoE), sirens, and other typical 12 or 24 V circuits in physical security work.

BETAConductor & Voltage-Drop Calculator

Sizes copper or aluminum conductors for low-voltage security and door-hardware circuits. Inputs are source voltage, current draw, one-way distance, and the voltage drop budget. Output is the recommended gauge plus the actual drop in volts and percent. Always verify against the device spec sheet and the applicable electrical code (CEC in Canada, NEC in the US).

DEVICE PRESET
Sets voltage and current. Adjust as needed.
CIRCUIT INPUTS
Use peak / inrush current for pass criteria, or steady-state for nominal sizing.
The Vdrop formula doubles this for round trip.
Common security-industry budget is 10% of source voltage.
RESULT
WITHIN BUDGET
Selected gauge holds the load with margin.
16
RECOMMENDED AWG
16
USING AWG
0.76 V
VOLTAGE DROP
6.3 %
DROP, PERCENT
11.24 V
VOLTAGE AT LOAD
1.20 V
ALLOWED VDROP
5.05 Ω
R PER 1000 FT
10 A
AMPACITY, EST.
FORMULA REFERENCE
Vdrop  = 2 × distance × current × R_per_kft / 1000
        = 2 × 150.0 ft × 0.500 A × 5.05 Ω/kft / 1000
Allowed= source voltage × allowed % / 100
        = 12 V × 10 % / 100 = 1.20 V
REFERENCE: COPPER RESISTANCE (Ω / 1000 ft @ 75°C)
6 AWG
0.49 Ω
~55 A
8 AWG
0.78 Ω
~40 A
10 AWG
1.24 Ω
~30 A
12 AWG
1.98 Ω
~20 A
14 AWG
3.14 Ω
~15 A
16 AWG
5.05 Ω
~10 A
18 AWG
8.05 Ω
~7 A
20 AWG
12.80 Ω
~5 A
22 AWG
20.40 Ω
~3 A
24 AWG
32.40 Ω
~2 A

BETA tool. Planning aid only. Verify against the device specification, the applicable electrical code, and the conduit fill / insulation rating of the cable type actually being installed. Aluminum entries derate by 1.61× the copper value at the same gauge.

When to use this

  • Pulling a mag lock or electric strike from a centralized power supply room and confirming the cable run will hold the load.
  • Verifying that a long REX or contact run will not collapse the operating voltage.
  • Sizing the spare conductors in a multi-pair pull so the gauge supports the longest device on the panel.
  • Confirming a cable spec sheet matches reality before approving a submittal.

What it does not replace

The calculator is a planning aid. It does not replace the device manufacturer's spec sheet, the controlling electrical code (CEC in Canada, NEC in the US), the insulation and jacket rating of the actual cable type being installed, or the conduit fill calculation for the pathway. It also does not compute inrush. Where a device specifies a peak inrush current well above its steady-state load, plug the inrush figure in and check the resulting drop separately.

BETA notes

This is a public BETA. The calculation engine uses standard NEC Chapter 9 Table 8 copper resistance values at 75°C and a 1.61× factor for aluminum. Ampacity values are conservative low-voltage planning numbers based on 30°C ambient and 60°C insulation. Refinements coming: per-circuit notes export, multi-device runs on a shared cable, voltage-drop on PoE Type 1, 2, 3, and 4 budgets, and CSV export of a building-wide circuit list. Feedback to [email protected].