PixelPower

WS2815 power calculator

WS2815 runs on 12 V with a per-pixel constant-current regulator, so its current per pixel is about a third of a WS2812B’s while its power is similar. That changes the supply you buy and how far a single feed reaches — both are estimated here for the length you type.

You enter

I’m building of at ,

Change anything — the answer updates as you type.

What you need

Calculated

82.8W

Estimated maximum power
i
Every channel of every pixel at full duty — the only figure a supply may be sized from. Based on the selected LED type and its preset figures; actual consumption depends on brightness, effects and conditions.

300 LEDs · 6.90 A at full white

could be 64.8 – 108 W

Recommended

12 V · 12.5A

Power supply
i
Sized from the top of the estimated range plus the controller, divided by 0.8 so the supply never runs at its thermal limit, then rounded up to a size that is actually sold.

The nearest size sold, with 20 % kept in reserve

Recommended

3

Power injection
i
Power weakens along the strip’s own copper. Feeding it in more than one place keeps the far end from dimming — this is the fewest evenly spaced feeds that stay inside your drop threshold.

Evenly spaced feed points, both ends included

Works with 3 feed points. The strip’s own copper carries about 4 A, so one feed can’t supply 6.90 A. Fed as recommended, the estimate stays within limits. One other thing to check below.

Needs attention

  • Each run draws up to 6.9 A, past the 4 A its own power trace is good for. Roughly 0.07 mm² of copper on a 10 mm strip — about the ampacity of 28 AWG. Push much past this into one end and the trace, or the connector feeding it, is what fails. Far below what the supply can deliver into a fault.

    Feed it at several points — the injection plan says how many — and fuse each feed just above its own worst-case current. The supply's own limit is far above what this copper survives.

  • "Strip 1" has no fuse planned. Around 15 A would suit it.

    Fuse every branch close to the supply. A supply’s own over-current threshold sits far above what LED wiring survives, so it is not protecting this cable.

How it’s wired

Estimated voltage along the strip at full white · Calculated
Supply 12 V · 12.5 A0 m2.5 m5 m
Feed point — as recommended Strip colour: within limits · colour shift likely · power won’t reachWorst point: 11.2 V of 12 V

More, when you want it

Detailsranges, standby draw, running cost, why this supply

What it draws

Estimated maximum current

6.90 A

could be 5.40 – 9.00 A

Estimated maximum power

82.8 W

could be 64.8 – 108 W

Worst case: every channel of every pixel at full duty — the only figure a supply may be sized from. Low confidence. Measuring one run at full white with a clamp meter replaces the estimate with a fact — the field is under Advanced settings.

Pixels
300 over 5 m
At typical content
2.61 A · 31.3 W

Average content draw is an estimate of what the installation usually does, not of what it can do. Use it for the electricity bill, never for a supply.

With every LED off
0.300 A · 3.60 W

This is the floor, not the load.

At brightness 255 would repeat the worst case above, so it is not shown.

Power supply

Recommended

12 V / 12.5 A (150 W)

Sized from 9.00 A — the top of the range for what is on this supply, not the headline figure — plus 0.15 A for the controller, with 20 % kept in reserve so the supply never runs at its thermal limit.

Show the arithmetic
Worst case, top of range
9.00 A
Controller
+ 0.15 A
Required continuously
9.15 A
Divided by 0.8 derating
11.4 A
Nearest size sold
12.5 A

Running cost

7.2 kWh / month· 2.2 €

Drawn from the wall at 35 % average content, 6 h a day. 5.0 kWh of it is the LEDs; 0.65 kWh is the ICs idling, 0.32 kWh the controller, and 1.2 kWh is lost in the supply.

Wiring3 feed points · no supply configured · fuses and cable

Where the power goes

One row per protected branch · Calculated
Power supply 12 V 15 A? 2 m of 1.5 mm² 6.90 A · 82.8 W Strip 1300 LEDs · 3 feed points

Fuse and cable are coloured by whether they suit the branch: suits it · check it · not protecting it. A rating with a ? is suggested — nothing is fitted yet. The taps that carry power into each strip are drawn above, not here.

Estimated voltage along the run

Evenly spaced, this run wants 3 feed points. If your strip sits at the thin end of its copper range and draws at the top of its current range, it would take 4 — unlikely to be both at once, but you buy the cable only once.

Supply
at the far end of the feed cable
12.0 V
Feed at 0 m
carries 6.9 A
11.7 V
At 5.0 m
unfed tail, 5.0 m
beyond the model

Beyond what this model can estimate. The model predicts a drop of 89 % of the feed voltage. Past the configured 25 % it is no longer describing a working installation, so no figure is given. The strip copper is the limiting element here: add injection points or feed from both ends. Verify against the actual strip and cable specifications.

Injection points1 on a 5.00 m run
Compare layouts what another feed would buy
No injection — fed at one end as planned
beyond the model
2 evenly spaced feeds
beyond the model
4 evenly spaced feeds
11.6 V(3.3 % drop)
6 evenly spaced feeds
11.8 V(1.4 % drop)
8 evenly spaced feeds
11.9 V(0.82 % drop)
Cable to each feed point 2 m of 1.5 mm²

The cable running to each injection point drops voltage too, and unlike the strip it carries the full current of that feed along its whole length. This is the tap after the strip’s power arrives — the cable from the supply itself is set per branch under Power distribution. Set the length to 0 to leave it out.

Thresholds where the bands sit

These are judgement calls, not physics. Around 10 % of the feed voltage, colour shift and dimming toward the far end become visible, and the rising ground shifts the data reference with it. Past 25 % the linear model is no longer describing a working installation, so no figure is reported at all. An architectural install holding a white tolerates far less than a party effect.

Power distribution

Total load82.8 Wacross 1 branch
Current6.90 Aworst case, every LED at full white
PixelPower recommends12 V · 12.5 Anone configured yet
Utilization—state a capacity to compare against

Power supply 12 V

  • Strip 1 6.90 A · 82.8 W · 11.7 V at the load

    no fuse planned — around 15 A would suit it. Cable: covers the branch (1.5 mm² or thicker).

Planning estimates, not an electrical design. A branch here is the cable from a supply to a load and the fuse protecting that cable — if you split that feed into several injection points, each tap needs its own protection too. Fuse and cable sizes are ordering guidance: real ampacity depends on insulation, bundling, ambient temperature and routing. PixelPower does not check any electrical code. Verify against the parts’ own datasheets and your local regulations.

Power supplies

No supply configured. PixelPower still recommends one — add a supply to check a capacity you already own, or to split the installation across several.

Layoutdraw the shape, several strips

1 strip has no shape, so it is not drawn — still counted in every total. Give it a shape below to place it.

5 m · 300 pixels. Drag a shape to move it. The picture is to scale; LEDs are drawn at their real spacing until they are too close together to tell apart.

ControllerGPIO, colour order, export for WLED

PixelPower can write the LED section of a WLED configuration from this project: the pixel count, one output per strip, the LED type, and a power budget from the supply you configured. Everything else in WLED is left exactly as you set it.

Outputs

  • Strip 1 300 LEDs from index 0 · WS281x · 111 fps

  • Worth knowing

    WLED's brightness limiter caps brightness to stay inside this budget. It is not a fuse and not a protective device.

    A config reset, a firmware update, a wrong LED count or a crash removes it. Size the supply and the fusing for full white regardless — PixelPower does.

Preview the configuration 300 LEDs · 10.0 A budget

80 % of the 12.5 A PixelPower recommends, since no supply capacity was stated.

{
  "hw": {
    "led": {
      "total": 300,
      "maxpwr": 10000,
      "ledma": 23,
      "ins": [
        {
          "start": 0,
          "len": 300,
          "pin": [
            16
          ],
          "order": 0,
          "type": 22,
          "rev": false,
          "skip": 0
        }
      ]
    }
  }
}

Sending writes the LED section of the controller’s configuration and applies it immediately. Nothing is sent unless you press the button. The power budget above is WLED’s brightness limiter — it caps brightness, it is not a fuse, and it does nothing about a short.

Parts7 lines · CSV and printable report

PixelPower states what each part has to do. It does not know what is on your shelf, so no product or supplier appears here unless you type one in.

  • LED strip Strip 1 — WS2815 (12 V RGB), 60 LED/m 5 m · You entered

    300 pixels at 12 V.

  • Power supply 12 V 12.5 A power supply 1 piece · Recommended

    9.15 A required ÷ 0.8 continuous derating = 11.437 A, rounded up to a 12.5 A supply.

  • Controller ESP32 LED controller 1 piece · You entered

    300 pixels across 1 output.

  • Cable 1.5 mm² copper 16 m · You entered

    Branch and injection runs, counted out and back.

  • Fuse and holder 15 A fuse with holder 1 piece · Recommended

    Smallest standard size above the worst case with the usual 1.25× margin. Nothing is planned for "Strip 1" yet.

  • Fuse and holder 7.5 A fuse with holder 3 pieces · Recommended

    One per injection point, sized for the busiest tap — an interior feed carries more than an end feed.

  • Connector Injection connector or solder joint 3 pieces · Recommended

    One per injection point, per run. Contacts add resistance — four at 5–30 mΩ are worth about a metre of strip copper.

Open the printable report

Ordering guidance, not a wiring specification. A fuse has to sit above the load it feeds and below what its cable and connectors can carry, and real ampacity depends on insulation, bundling and how a run is routed. Check against the parts’ own datasheets and your local regulations.

Advanced settingsthe strip itself, how you drive it, your own figures

The strip itself

How you drive it

Where the power figures come from

Assumptions6 figures PixelPower had to guess at
This result rests on 6 assumptions show

These are the figures PixelPower had to guess at, and they are why the range above is as wide as it is. Replace any of them with your strip’s datasheet — or better, a clamp-meter reading at full white — and the uncertainty it contributes disappears.

  • 7.33 (5.80 – 9.60) Assumed · Low confidence

    Back-derived from 18–30 mA per pixel at full white (23 mA typical). WS2815 drives its dies from per-pixel constant-current regulators on a 12 V rail; real figures vary by vendor and IC revision, so measure before trusting this.

  • 1.00 (0.600 – 1.20) Assumed · Low confidence

    Comparable per-pixel idle current to a 5 V part, but 2.4× the idle power, because P = V·I. 1000 pixels idle is roughly 12 W.

  • 0.600 (0.450 – 0.900) Preset · Low confidence

    A 10 mm strip with roughly 1 oz copper on both the +V and GND traces. The default, and about what most branded reels measure.

  • 4.00 (2.00 – 6.00) Preset · Low confidence

    Roughly 0.07 mm² of copper on a 10 mm strip — about the ampacity of 28 AWG. Push much past this into one end and the trace, or the connector feeding it, is what fails. Far below what the supply can deliver into a fault.

  • 0.350 (0.100 – 0.550) Assumed · Low confidence

    Typical animated content averages roughly 35 % of full white. Sparkle effects run near 10 %, slow rainbows near 55 %. Strongly content-dependent.

  • 150 (80.0 – 250) Assumed · Low confidence

    An ESP32-class controller with Wi-Fi active, 80–250 mA depending on the board and transmit duty.

82.8 W needs 12 V · 12.5 A

Reference figures, 5 m at full white

Computed by the same engine as the calculator above, so they agree with it. Ranges reflect the spread between vendors. Verify against the actual strip and supply specifications.

StripLED/mPixelsCurrentPowerSupply
WS2815 (12 V RGB)30150 3.45 A (2.70–4.50)41.4 W12 V · 8.5 A
WS2815 (12 V RGB)60300 6.90 A (5.40–9.00)82.8 W12 V · 12.5 A
WS2815 (12 V RGB)144720 16.6 A (13.0–21.6)199 W12 V · 30 A
WS2812B (5 V RGB)30150 9.15 A (7.29–9.18)45.8 W5 V · 15 A
WS2812B (5 V RGB)60300 18.3 A (14.6–18.4)91.5 W5 V · 25 A
WS2812B (5 V RGB)144720 43.9 A (35.0–44.1)220 W5 V · 60 A

What is different about WS2815

A WS2815 pixel draws roughly 23 mA at full white — vendors and IC revisions spread that over about 18–30 mA, so PixelPower carries the range rather than a single figure and marks it low-confidence until you measure. At 12 V that is about 0.28 W per pixel, comparable to a 5 V part: the regulator burns the difference between the rail and the die voltages as heat.

Because the current is lower, the same copper carries a run about three times as long before the drop matters. Because the rail is 12 V, a given drop in volts is a smaller fraction of it. Both effects are why a 12 V strip needs fewer injection points — the calculator shows how many, for your length and density.

The idle power is 2.4× a 5 V strip’s for the same pixel count, simply because P = V·I: a thousand idle WS2815 pixels are roughly 12 W.

The regulator hides nothing

A 5 V strip fades gracefully as the rail sags — blue first, then green, then red. A WS2815 regulator holds its current constant until the rail reaches roughly 9–11 V and then the pixels simply stop. PixelPower treats that region as beyond the model and reports no figure for it rather than a misleadingly small one.

Questions people ask

How much current does a WS2815 strip draw per metre?

At 60 LEDs/m, about 1.4 A per metre at full white — 60 × 23 mA — with an estimated range of roughly 1.1–1.8 A/m across vendors. At 12 V that is about 16.6 W/m. Verify against the actual strip and supply specifications before you buy or build.

What power supply does a 5 m WS2815 strip need?

For 300 pixels PixelPower estimates 6.9 A at full white (range 5.4–9.0 A) and recommends a 12 V supply of 12.5 A: the top of the range plus the controller, divided by 0.8, rounded up to a size that is sold. Open the calculator above with your own length to see the steps.

Does WS2815 need power injection?

Less often than a 5 V strip, but yes on long runs. The current is lower and the rail is 12 V, so a single feed reaches roughly three times further — the calculator estimates the drop along your run and the fewest evenly spaced feeds that keep it within the configured threshold.

Is the WS2815 figure a measurement?

No — it is back-derived from the 18–30 mA per pixel commonly measured on real strips, so PixelPower marks it as an assumption with low confidence. A clamp-meter reading of your own strip at full white replaces it, and the field for that is under Advanced settings.

Take the plan further

The answer above is the start. The full planner draws the layout, plans the branches, fuses and cable from each supply, writes a WLED configuration from the plan and produces a parts list and a printable report — all from the numbers you just typed, and nothing to sign up for.

Open the full plannerWS2815 power, explainedVoltage drop along an LED strip