LED Strip Power Supply Calculator — Watts, Amps, Injection Points
Who this is for: For WS2812/SK6812 and analog strip builds: the two classic failures are an undersized 5 V supply and a long strip with voltage sagging at the far end.
Power supply sizing for LED strips: enter length and W/m to get total watts, total amps, the PSU wattage to buy with headroom, and how many power injection points the strip needs.
Quick answer: Total power = length × watts per meter; amps = watts ÷ supply volts. A 5 m strip at 14.4 W/m draws 72 W — 14.4 A at 5 V — so buy a 90 W (18 A) supply for 20% headroom, and inject power from both ends if you're running close to full brightness. And no, the ESP32 does not power the strip: the GPIO provides only the data signal, while the supply feeds the strip directly through a common ground.
From the strip spec — 5 V: 7–18 W/m · 12 V: 4.8–14.4 W/m
Don't run a PSU at 100% — 20% is the usual margin
| What this means in practice | Number |
|---|---|
| PSU wattage to buy (with headroom) | 86 W |
| Current per injection point (5 m segments) | 14.4 A |
| Max LEDs a single ESP32 GPIO can drive directly | 1 (signal only) |
| Formula | W = length × W/m · A = W ÷ V |
|---|---|
| PSU headroom | +20% minimum |
| Injection cadence | every ~5 m (more on 5 V high-density) |
| ESP32 role | data signal only, ~12 mA max per GPIO |
| Long runs | prefer 12 V or 24 V strips over 5 V |
How to size an LED strip power supply
LED strip power math starts with one spec from the strip's own listing — watts per meter at full brightness, per meter of strip, not per meter of LED — and multiplies by your length. From there it's Ohm's law split in two: total amps at your chosen voltage, and the PSU wattage you should actually order, which means adding headroom. A 5 V strip wants 20% minimum; a supply run at 100% of rating is a supply running hot, and cheap ones derate their own label.
The second half of the problem isn't the total, it's the distribution. Copper traces inside a 5 m strip have real resistance — the far end of an unreinforced 5 V strip can see under 4 V at full white, which reads as a pink/red gradient. The fix is multiple power injection points (clip +5 V and GND into the strip every ~5 m, feeding back toward the start), and this calculator returns the number of injection points for your length as a starting plan.
For ESP32 builders the last piece is the interface: the supply powers the strip, the ESP32's GPIO carries only the data signal, and both share a ground. Addressable 5 V strips technically accept a 3.3 V data signal, but many do it marginally — through a short wire it usually works, over a long one it flickers. A level shifter (or one channel of a spare gate powered at 5 V) makes it reliable, and a 300–500 Ω resistor in series with the data line protects the first pixel from ringing. That data-line advice is different from a plain RGB analog strip, which needs MOSFETs instead of a data signal — one MOSFET per color channel, and the supply does the heavy lifting there too.
Common uses
- Choosing the PSU for a 5 m WS2812B strip behind a desk or TV
- Planning power injection for a 20 m run along a room ceiling
- Checking whether a 12 V 3 A brick can feed two 2 m strips in parallel
- Sizing the fuse to put in line with a big 5 V strip (hint: at the PSU's amp rating)
- Deciding between 5 V addressable and 12 V analog strips for a long installation
Specs from real strip listings
5 V addressable: 30 LED/m ≈ 9 W/m, 60 LED/m ≈ 18 W/m (full white; typical patterns use a third of that). 12 V analog: 30 LED/m ≈ 7.2 W/m, 60 LED/m ≈ 14.4 W/m. 24 V strips run lower current per watt — for runs over ~10 m, 24 V is the sane choice because amps scale down with voltage. Watts per meter always refers to full white, all channels on — movies and color patterns draw a fraction, but size the supply for full white anyway: the day you write a 'turn everything on' test pattern is the day an undersized supply gets hot.
The ESP32's part (and only its part)
ESP32's job is the data signal: one GPIO, under 12 mA, never the strip's power. Two things make the interface robust: a common ground between the strip's supply and the ESP32 (without it, the data signal has no reference and nothing works), and a level-shifted data line for 5 V strips. Wires matter too: from the PSU to the strip, use short thick wires (18–20 AWG for a few amps) — the strip's own copper is the thin part you're compensating for with injection points.
Frequently Asked Questions
How many LEDs can an ESP32 drive?
What power supply do I need for a 5 m WS2812B strip?
Why does the far end of my LED strip look dimmer or pink?
Can I power the strip from the ESP32's 5 V pin?
Do I need a level shifter for a 5 V LED strip with an ESP32?
Should I fuse a big LED strip?
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