The transformer and wire calculator.
Add up your fixtures, set the longest wire run and the wire gauge and see the transformer to look at, the voltage drop, the voltage at the last fixture and the longest run each wire can handle. Free, with no signup.
- Transformer size
- Voltage drop
- Free, no signup
Transformer to look at0 W
Total load0 W
- Voltage drop on the longest run
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- Voltage at the last fixture
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- Smallest wire that stays under 10%
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- Longest run for this wire
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Saved. It will travel with your estimate request below.
Planning math for a 12 volt system using round-trip wire resistance and a common 80 percent load rule. Real systems also depend on connections, tap settings and fixture types, and a technician measures before anything is bought.
Four things that decide a system.
Total load
Add up the watts of every fixture and leave about 20 percent spare.
Run length
The longer the wire, the more voltage it loses along the way.
Wire gauge
Heavier wire loses less, which keeps the last fixture bright.
Layout
Splitting a long run into two shorter ones is often the best fix.
Learn more about each one.
Smart Controls and SystemsTransformer and Wiring UpgradesGood light starts with good power.
Design and PlanningLighting Plans and ZonesA map for the light.
Smart Controls and SystemsLED ConversionsBrighter for less.
Service and CommercialLighting Repair and TroubleshootingFind the cause, not just the symptom.
Paths, Steps and SafetyDriveway and Entrance LightingLight the way in.
Design and PlanningLighting Retrofits and UpgradesKeep what's good, fix what isn't.Transformer and Wire Calculator questions
How many fixtures does my yard need?
It depends on what you want to light, not on square footage. A good design uses fewer, well-aimed fixtures. Our Light Designer gives a planning count, and a walk-through gives the real one.
Are your estimates free?
Yes. Estimates are free and come in writing with the plan, the fixtures, the controls and the price. Fill in the form on any page, or call or text 615-431-3789, and we will set up a visit at dusk or review your photos.
Do you repair lights you did not install?
Yes. We test the transformer, wire and fixtures, find the cause of dark or dim sections and explain the repair or upgrade options in writing.
Want it measured for real?
A technician with a meter measures voltage at your fixtures and sizes the transformer and wire for your yard.