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Gate opener wire size calculator
Free tool by the GateOpenerLab editorial team. Last updated . No sign-up; your answers stay in the page address so you can share the result.
Quick answer
Pick the smallest wire whose voltage drop stays within your limit, often 3%. Voltage drop is 2 × one-way distance × current × the wire's resistance per 1,000 ft, divided by 1,000. Long low-voltage runs need much thicker wire than 120 V runs. For any 120/240 V circuit, hire a licensed electrician.
Openers with this current draw
Eagle-I Residential Slide Gate Operator
- Up to 18 ft and 300 lb (maker's rating)
- UL 325 compliant, per the maker
- $1,300–$1,400 at the time of writing (checked Nov 2026)
Eagle-100 Residential/Light Commercial Swing Gate Operator
- Up to 18 ft and 600 lb (maker's rating)
- UL 325 compliant, per the maker
- $2,200–$2,300 at the time of writing (checked Nov 2026)
Eagle-1000 FR Slide Gate Operator (Foot Release)
- Up to 27 ft and 600 lb (maker's rating)
- UL 325 compliant, per the maker
- $1,700–$1,800 at the time of writing (checked Nov 2026)
Eagle-1000 FSC Slide Gate Operator (Fail-Secure)
- Up to 27 ft and 600 lb (maker's rating)
- UL 325 compliant, per the maker
- $1,600–$1,700 at the time of writing (checked Nov 2026)
Eagle-200 1/2 HP Swing Gate Operator
- Up to 20 ft and 750 lb (maker's rating)
- UL 325 compliant, per the maker
- $2,600–$2,700 at the time of writing (checked Nov 2026)
Eagle-2000 FSC Commercial Slide Gate Operator
- Up to 45 ft and 1,000 lb (maker's rating)
- UL 325 compliant, per the maker
- $2,000–$2,100 at the time of writing (checked Nov 2026)
Eagle-II Residential Swing Gate Operator
- Up to 14 ft and 400 lb (maker's rating)
- UL 325 compliant, per the maker
- $1,800–$1,900 at the time of writing (checked Nov 2026)
Eagle-2000 APT 1 HP Slide Gate Operator (Fail-Secure)
- Up to 50 ft and 2,500 lb (maker's rating)
- UL 325 compliant, per the maker
- $2,400–$2,500 at the time of writing (checked Nov 2026)
Eagle-2000 APT DM Dual 1 HP Slide Gate Operator (Fail-Secure)
- Up to 50 ft and 2,500 lb (maker's rating)
- UL 325 compliant, per the maker
- $3,400–$3,500 at the time of writing (checked Nov 2026)
Learn more: Gate opener wiring guide
How the calculator works
Current flowing through a long wire loses voltage on the way, out and back. Too much drop and a motor runs hot, starts slowly or a control board resets. The calculator works out the drop for every common wire size and picks the smallest one that stays within your limit.
The formula
voltage drop (V) = 2 × one-way distance (ft) × current (A) × resistance (Ω per 1,000 ft) ÷ 1,000
drop % = voltage drop ÷ system voltage × 100
Resistance comes from NEC Chapter 9, Table 8 (uncoated copper at 75 °C, stranded where the table lists both):
| AWG | Ω per 1,000 ft |
|---|---|
| 18 | 7.95 |
| 16 | 4.99 |
| 14 | 3.14 |
| 12 | 1.98 |
| 10 | 1.24 |
| 8 | 0.778 |
| 6 | 0.491 |
| 4 | 0.308 |
| 3 | 0.245 |
| 2 | 0.194 |
The calculator checks sizes down to 4/0. If even 4/0 is not enough, move the power supply closer or raise the voltage.
Limits of this tool
- Voltage drop only. It does not check ampacity, breaker size, burial depth, conduit fill or GFCI rules. Those are set by the NEC and your local code.
- Motors draw several times their running current for a moment when they start. The maker's wire chart, if your manual has one, already allows for that.
- Copper only. Aluminum wire has higher resistance.
- For these small sizes we use DC resistance for AC too. An electrician may use NEC Table 9 for AC runs.
Frequently asked questions
What size wire do I need for a gate opener?
It depends on the voltage, the current the opener draws and how far the wire runs. Low-voltage runs of a few hundred feet often need much thicker wire than you expect. Enter your numbers above to get the AWG size that keeps the voltage drop within your limit.
Why does low-voltage wire need to be so thick?
For the same current and wire, the drop in volts is the same at any system voltage. At 12 V, losing 1 volt is over 8 percent; at 120 V it is under 1 percent. Low-voltage motors also draw more current for the same work. So a 12 or 24 V opener far from its power supply needs heavier wire.
What voltage drop is acceptable?
For 120 V branch circuits, an informational note in the NEC suggests about 3 percent, and 5 percent for feeder and branch together. It is a recommendation, not a rule. For low-voltage openers, follow the wire chart in your opener’s manual if it has one.
Is the distance one way or round trip?
Enter the one-way distance from the power supply to the opener. The formula already doubles it for the return wire.
Can I run the 120 V wire to my gate myself?
We recommend a licensed electrician for any 120/240 V circuit. Burial depth, conduit, breaker size and GFCI protection are set by code and your local inspector, and this calculator does not cover them.
Sources for the numbers
- NFPA 70 (NEC) Chapter 9, Table 8, Conductor Properties (DC resistance at 75 °C) (opens in a new tab) · checked Nov 2026
- NEC 210.19(A) informational note on voltage drop (3% branch, 5% total), as summarized by ExpertCE (opens in a new tab) · checked Nov 2026Informational recommendation, not a code requirement.
- Eagle Access Control Systems product pages and cut sheets (gate capacity, current draw) (opens in a new tab) · checked Nov 2026
- Gate Operators Direct product pages (prices and specs per product) (opens in a new tab) · checked Nov 2026