Cost & material estimator
Landscape Lighting Planner
Low-voltage lighting is genuinely DIY. What sinks installs is transformer sizing and voltage drop — fixtures at the end of a long run getting 9 V and looking visibly dimmer than the rest.
- Total load and a transformer sized with real headroom
- Voltage drop on your longest run, with the formula shown
- A gauge comparison table for your specific run
- Fixture, cable and connector quantities
- Material cost against installed pricing
- A clear line between DIY and electrician work
Landscape Lighting Planner — interactive tool
Fixtures
A few well-placed fixtures beat many. Restraint reads as expensive here.
Along a route, staggered rather than lining both sides like a runway.
Into a tree canopy or up a wall. The highest-impact fixture per dollar.
Across a flat surface — a fence, a screen, a garage door — for a broad glow.
Where a level change is a trip hazard after dark. Safety first, effect second.
Under a cap or a bench edge, lighting the surface rather than the eye.
A single specimen plant or a feature. Use sparingly — every spot dilutes the last.
Cable runs
Splitting the load across more runs cuts the voltage drop on each.
If not, installing one is an electrician's job and often the largest single cost in a first installation.
Region
14 fixtures · 72 W
Your landscape lighting plan
transformer, running at 72% of rating with 28% headroom
- Total load
- 72 W
- Cable
- 276 ft 12/2
- Voltage drop
- 0.58 V
- At the far end
- 11.42 V
- Materials
- $1,173
- Installed
- $2,647+
Voltage drop: 0.58 V drop over 120 ft on 12/2 cable — fixtures at the end see about 11.42 V, which is comfortably inside the usable range for 12 V LED.
Home & Garden Living · homeandgarden.living/tools/landscape-lighting-calculator
Low voltage is the DIY-safe half of outdoor lighting
12 V cable carries no shock risk in normal handling and can be buried shallow. That's what makes this a genuine DIY project. The line-voltage side - the outlet the transformer plugs into - is a different matter entirely.
Aim it after dark, weeks later
Install the fixtures loosely, then come back after dark - ideally a few weeks later once planting has settled - and aim everything properly. A yard looks completely different lit, and almost every fixture ends up pointing somewhere other than planned.
Bury the cable, but call 811 first
Low-voltage cable is typically buried 6 in deep. That's shallow, and it is still deep enough to reach an irrigation line or a shallow service. Utility locating is free and it takes several days.
| Item | Quantity | Cost |
|---|---|---|
| Path lightAlong a route, staggered rather than lining both sides like a runway. | 8 x 4 W | $368 |
| UplightInto a tree canopy or up a wall. The highest-impact fixture per dollar. | 4 x 7 W | $232 |
| Wall washAcross a flat surface — a fence, a screen, a garage door — for a broad glow. | 2 x 6 W | $124 |
| 100 W transformer with timer and photocell72 W load = 72% of rating, leaving 28% headroom | 1 | $102 |
| 12/2 direct-burial low-voltage cable | 276 ft | $304 |
| Waterproof wire connectorsSilicone-filled connectors rated for direct burial. Ordinary wire nuts corrode within a season. | 18 | $43 |
| Materials total (DIY) | $1,173 | |
The voltage-drop formula, published
Voltage drop = (run length in feet × watts on that run) ÷ cable constant. Your run: (120 × 36) ÷ 7500 = 0.58 V, leaving 11.42 V at the far fixture. Most 12 V LED fixtures work happily down to about 10.5 V; below that they visibly dim and shift yellow.
| Cable gauge | Constant | Drop on your run |
|---|---|---|
| 16/2 | 2,200 | 1.96 V → 10.04 V |
| 14/2 | 3,500 | 1.23 V → 10.77 V |
| 12/2 | 7,500 | 0.58 V → 11.42 V |
| 10/2 | 11,920 | 0.36 V → 11.64 V |
| 8/2 | 18,960 | 0.23 V → 11.77 V |
- Fixtures
- 14
- Runs
- 2
- Watts per run
- 36 W
- Install time
- ~9.5 hr
Your shopping list
$1,173Fixtures
Power
Take these numbers further
What this estimate assumes
- · Fixture wattages are typical 2026 LED figures from the published table on this page.
- · The transformer is sized so the load is at most 80% of its rating, then rounded up to a standard size.
- · Voltage drop uses the standard low-voltage formula: (run length × watts on the run) ÷ cable constant, with the load assumed split evenly across your runs.
- · 12 V LED fixtures are treated as acceptable down to about 10.5 V. Check your specific fixture's rated range.
- · Cable is calculated at your longest run × number of runs, plus 15% for routing and slack.
- · This covers low-voltage work only. The exterior GFCI outlet the transformer plugs into is line-voltage work for an electrician.
Low-voltage lighting is genuinely DIY. What sinks installs is transformer sizing and voltage drop — both calculated here, with the formula published.
Landscape lighting is one of the highest-return improvements available to a yard, and one of the few outdoor electrical jobs a homeowner can genuinely do themselves. Twelve-volt cable carries no shock risk in normal handling and can be buried shallow. That's what makes it accessible.
It also fails in a specific, predictable way that almost nobody warns about. Run twelve fixtures off a hundred and fifty feet of thin cable and the ones at the far end receive perhaps nine volts instead of twelve. They look visibly dimmer, and the colour shifts noticeably yellow. People assume they got a bad batch of fixtures.
It's voltage drop, and it's entirely calculable before you buy anything using the standard cable-constant formula — which this publishes, along with a table showing what every gauge would do on your specific run. The other calculation is transformer sizing: run one at its rated capacity and it has no headroom for the fixtures you'll inevitably add.
One boundary worth stating clearly. Everything downstream of the transformer is low-voltage DIY work. The transformer itself plugs into a weather-resistant, GFCI-protected exterior outlet, and installing one of those is line-voltage work — licensed electrician territory in most jurisdictions, and frequently the largest single cost in a first landscape lighting installation.
The voltage-drop formula
Voltage drop equals the run length in feet multiplied by the watts on that run, divided by the cable constant. The constants are fixed properties of the cable gauge, and they're published below.
So a hundred and fifty foot run carrying sixty watts on 14/2 cable drops (150 × 60) ÷ 3500 = 2.6 volts, leaving 9.4 volts at the far fixture. On 12/2 the same run drops 1.2 volts, leaving 10.8 — which is inside the usable range for most 12 V LED fixtures. That single change of cable is the difference between an installation that looks even and one that doesn't.
Three levers reduce drop: heavier cable, shorter runs, or splitting the load across more runs from the transformer. Splitting is usually the cheapest, and it has the additional benefit that a fault on one run doesn't take out the whole scheme.
| Gauge | Constant | Typical use |
|---|---|---|
| 16/2 | 2,200 | Very short runs and small loads only |
| 14/2 | 3,500 | Short runs under about 100 ft with light loads |
| 12/2 | 7,500 | The sensible default for most residential schemes |
| 10/2 | 11,920 | Long runs, or heavy loads on a single run |
| 8/2 | 18,960 | Very long runs; rarely needed on a residential scheme |
Cable constants for the standard low-voltage voltage-drop formula: drop = (run length × watts) ÷ constant.
Sizing the transformer
Add up the wattage of every fixture, then size the transformer so that total is no more than about 80% of its rating. A transformer running at its rated capacity has no margin, runs hotter, and gives you nowhere to go when you want to add two more uplights next spring — which you will.
Standard sizes are 100, 150, 200, 300, 600 and 900 watts. The price difference between adjacent sizes is small relative to the cost of replacing one, so err upward.
Get one with both a timer and a photocell. A photocell turns the lights on at dusk regardless of the season, which a fixed timer doesn't — and the difference matters most in spring and autumn when sunset moves fastest.
Design restraint beats fixture count
Landscape lighting is one of the few areas where spending less looks better. Two uplights into a good tree do more than a dozen path lights lining a route on both sides like an airport runway — which is the single most common landscape lighting mistake and the one that immediately reads as amateur.
Stagger path lights, alternating sides, and space them further apart than feels right. Their job is to indicate the route, not to illuminate it. Save the brightness for uplighting something worth looking at.
And aim everything after dark, weeks later. Install the fixtures loosely, live with them for a while — ideally until any new planting has settled — then go out at night and aim them properly. A yard looks completely different lit, and almost every fixture ends up pointing somewhere other than where it was planned.
- Warm colour temperature — 2700K or lower. Cool white outdoors looks institutional.
- Hide the source, show the effect. A visible bulb is glare, not lighting.
- Use silicone-filled, direct-burial-rated connectors. Ordinary wire nuts corrode within a season.
- Bury cable about 6 in deep, and call 811 first — that's still deep enough to reach an irrigation line.
What this tool assumes
Every number this tool produces rests on these. Change your inputs and they change with you.
- Fixture wattages are typical 2026 LED figures from the published table on this page.
- The transformer is sized so the load is at most 80% of its rating, then rounded up to a standard size.
- Voltage drop uses the standard formula: (run length × watts on the run) ÷ cable constant, with the load assumed split evenly across your runs.
- 12 V LED fixtures are treated as acceptable down to about 10.5 V. Check your specific fixture's rated range.
- Cable is calculated at your longest run × number of runs, plus 15% for routing and slack.
- This covers low-voltage work only. The exterior GFCI outlet is line-voltage work for an electrician.
Mistakes that cause rework
Each of these costs money or a whole weekend to undo.
Ignoring voltage drop entirely
The most common cause of an uneven-looking installation. Fixtures at the end of a long thin run get visibly less light and shift yellow, and people blame the fixtures.
Running the transformer at its rating
No headroom for the fixtures you'll add, and it runs hot. Size it so the load is at most 80% of the rating — the price difference between sizes is small.
Path lights lining both sides of a route
It reads as a runway. Stagger them, alternate sides, and space them further apart than feels right. Their job is to indicate the route, not light it.
Ordinary wire nuts on buried connections
They corrode within a season and the fixture goes dark for no visible reason. Silicone-filled, direct-burial-rated connectors only.
Aiming fixtures in daylight
A yard looks completely different lit. Install loosely, come back after dark weeks later, and aim everything then. Almost every fixture moves.
Cool-white bulbs
2700K or lower. Cool white outdoors makes planting look grey and the whole scheme look like a car park.
Safety & honest limits
- This page covers low-voltage (12 V) work only. Installing the exterior GFCI outlet the transformer plugs into is line-voltage work — a licensed electrician's job in most jurisdictions, and often permitted.
- The transformer must plug into a weather-resistant, GFCI-protected exterior receptacle. Never use an indoor outlet with a cable run through a window or door.
- Call 811 before burying cable. Six inches is shallow, and it's still deep enough to reach irrigation lines and shallow services.
- Use direct-burial-rated cable and silicone-filled connectors. Ordinary indoor materials fail quickly outdoors and can fail unsafely.
- Don't exceed the transformer's rated capacity, and don't run it continuously at its rating.
- Costs are estimates, not quotes.
Frequently asked questions
What size transformer do I need for landscape lighting?
Add up every fixture's wattage and choose a transformer where that total is no more than about 80% of the rating. Fourteen LED fixtures at around 5 W each is 70 W, which suits a 100 W transformer — but a 150 W leaves room to add more, and the price difference is small.
How do you calculate voltage drop in landscape lighting?
Voltage drop = (run length in feet × watts on that run) ÷ cable constant. The constants are 3,500 for 14/2, 7,500 for 12/2 and 11,920 for 10/2. Keep the far fixture above about 10.5 V. The full table for your run is on this page.
What gauge wire for low voltage landscape lighting?
12/2 is the sensible default for most residential schemes. Go to 10/2 for long runs or heavy loads; 14/2 is only adequate for short runs with light loads. The gauge comparison for your specific run is calculated on this page.
How deep do you bury landscape lighting wire?
About six inches is standard for direct-burial low-voltage cable — deep enough to be out of the way of ordinary garden work. Call 811 first anyway: six inches still reaches irrigation lines and shallow services.
Can I install landscape lighting myself?
The low-voltage side, yes — that's what makes this a good DIY project. The exterior GFCI outlet the transformer plugs into is line-voltage work and is an electrician's job in most jurisdictions. If you already have that outlet, the rest is genuinely straightforward.
How much does landscape lighting cost?
DIY, roughly $60–110 per fixture installed including the share of transformer and cable, so a 14-fixture scheme runs about $900–1,500 in materials. Professionally installed, typically $150–300 per fixture. Adding an exterior outlet, if you need one, is separate.
Why are some of my landscape lights dimmer than others?
Almost always voltage drop. Fixtures furthest from the transformer on a long or thin cable run receive less voltage, so they're dimmer and shift yellow. Heavier cable, shorter runs, or splitting the load across more runs all fix it.
Last reviewed July 25, 2026 · Home & Garden Living
Keep planning
Built to work together — each one picks up where this leaves off.
Run the numbers
Next steps
Finished here? Keep the momentum.