LED Strip Wiring Guide
Calculate the current draw, choose the right wire gauge and select the correct fuse for any 12V or 24V LED strip installation. Covers van builds, shed lighting, workshop strips and under-cabinet installs, with a worked example for a 5 m strip run.
Last updated: May 2026
The scenario
You want to install 5 m of 12V LED strip lighting in a camper van, workshop or shed. The strip is rated at 14.4 W/m (a common value for mid-brightness COB or SMD5050 strips). You need to know the total current, what wire to use for the run from the power supply to the strip, and which fuse to fit to protect the wire. Each step below leans on a different tool from the Electronics Hub, so you can follow along and confirm every figure as you go.
Step 1: Calculate total power and current
Multiply the strip's watt-per-metre rating by the total strip length to get total power. Divide by the supply voltage to get current in amps.
Power = 14.4 W/m × 5 m = 72 W | Current = 72 W ÷ 12 V = 6 A
Common LED strip watt ratings and their currents at 12V and 24V:
| Strip rating (W/m) | 5 m at 12V (A) | 5 m at 24V (A) | Typical type |
|---|---|---|---|
| 4.8 W/m | 2.0 A | 1.0 A | Low-brightness SMD3528 |
| 9.6 W/m | 4.0 A | 2.0 A | Mid SMD5050 RGB |
| 14.4 W/m | 6.0 A | 3.0 A | High SMD5050, COB single colour |
| 24 W/m | 10.0 A | 5.0 A | High-density COB, trade strip |
Use the calculator: Enter total power (W) and supply voltage into the Watts / Volts / Amps Calculator to confirm current, or use it in reverse if you know the current and voltage.
Step 2: Choose wire gauge for the run
Wire gauge depends on the current and the length of the run from the power supply or battery to the strip. For LED strips, keep the voltage drop under 3% of the supply voltage, otherwise strips at the far end will be dimmer than at the start.
For 12V: 3% of 12V = 0.36V drop allowed. For 24V: 3% of 24V = 0.72V allowed. 24V strips are more tolerant of long runs because the absolute voltage loss is less significant.
| Current (A) | Run to strip (m) | 12V recommended wire | 24V recommended wire |
|---|---|---|---|
| 2 A | up to 8 m | 0.75 mm² (AWG 18) | 0.5 mm² (AWG 20) |
| 4 A | up to 5 m | 1.5 mm² (AWG 15) | 0.75 mm² (AWG 18) |
| 6 A | up to 3 m | 1.5 mm² (AWG 15) | 1.0 mm² (AWG 17) |
| 6 A | 3 to 6 m | 2.5 mm² (AWG 13) | 1.5 mm² (AWG 15) |
| 10 A | up to 3 m | 2.5 mm² (AWG 13) | 1.5 mm² (AWG 15) |
Use the calculator: Enter your current, one-way run length, supply voltage (12 or 24), copper wire and 3% drop limit into the Wire Gauge Calculator. The result shows the minimum wire size and the actual voltage drop in volts and percent.
Step 3: Select the fuse
Fit a fuse rated at 125% of the strip's normal current, then round up to the next standard blade fuse or in-line fuse size. The fuse protects the wire, not the strip, a fuse rated too high will not blow before the wire overheats.
| Strip current (A) | 125% value | Fuse to use |
|---|---|---|
| 2 A | 2.5 A | 3 A |
| 4 A | 5.0 A | 5 A |
| 6 A | 7.5 A | 7.5 A (or 8 A) |
| 10 A | 12.5 A | 15 A |
Place the fuse as close to the power supply or battery terminal as possible, ideally within 15 cm of the positive output. An in-line blade fuse holder is standard for LED strip wiring.
Use the calculator: Enter the circuit's normal current into the Fuse / Breaker Sizing Calculator to confirm rating.
Step 4: Choose and size the power supply (if mains-powered)
If you are running from a 230V mains outlet rather than a 12V battery, you need a DC power supply (PSU) or LED driver. Size it for at least 120% of the strip's total power to avoid running at full load continuously, which reduces PSU lifespan.
Minimum PSU power = 72 W × 1.20 = 86.4 W → choose a 100 W PSU
| Total strip power (W) | Minimum PSU (W) | Standard PSU to buy |
|---|---|---|
| 24 W | 29 W | 30 W or 60 W |
| 48 W | 58 W | 60 W |
| 72 W | 86 W | 100 W |
| 120 W | 144 W | 150 W or 200 W |
For dimmer compatibility: most LED strips work with PWM dimmers placed between the PSU and the strip. The PWM dimmer must be rated for the full current of the strip, not just the dimmed current.
Common mistakes
- Undersizing the wire for long runs: using 0.75 mm² for a 6 A strip on a 5 m run causes a 1.5 V drop at the strip end, the last metre will be noticeably dimmer. Use 2.5 mm² for that run.
- No fuse on a direct battery connection: in a van build, any positive wire from the battery without a fuse is a fire hazard. Fit a fuse within 15 cm of the battery terminal even for a small strip.
- Connecting the strip at one end only for runs over 5 m: long strips have resistance, so the far end dims under voltage drop. Feed from both ends with equal wire lengths, or split the run into two shorter sections each fed from the PSU.
- Mismatching strip voltage: connecting a 24V strip to a 12V supply gives about 25% brightness. Connecting a 12V strip to a 24V supply will instantly destroy the LEDs. Check the label before connecting.
- Running max-wattage strips in enclosed channels: high-density strips (24 W/m+) generate significant heat. Aluminium extrusion channels act as heatsinks and are not optional at these densities.
How an LED strip pulls the bench calculators together
An LED strip installation is not a single calculation: it is a build sequence where each step feeds the next. This is where the DC calculator chain comes together into something you can actually wire up.
- Start with the base physics. Voltage, current, resistance and power underpin everything. The Ohm's Law calculator is the foundation the rest of the chain grows from.
- Size the individual LED resistors (for indicator LEDs alongside the strip). Any status or indicator LED wired in parallel with the strip still needs a series resistor. Use the LED resistor calculator for those.
- Work out total power and current draw. Multiply the strip's W/m rating by length, then divide by supply voltage. The Watts / Volts / Amps calculator confirms current and lets you sanity-check the supply capacity.
- You are here: the practical build. Total current in hand, wire the strip correctly: choose wire gauge for the run, size the fuse, inject power where the run demands it. This guide is that assembly step.
- Check the voltage drop on the wire run. A long run from the supply to the strip drops voltage and dims the far end. The voltage drop calculator tells you how much drop to expect and confirms whether your wire gauge is sufficient before you crimp a single terminal.
- Size the battery if running off-grid. For van or shed builds not on mains, total current and run time give you the battery capacity you need. The battery life calculator works that out.
On a long 12 V strip, feeding power from one end only leaves the far end dimmer and warmer in colour, even on good wire. Inject at both ends instead and the strip snaps to uniform output. It is the clearest example of voltage drop you can see with your own eyes, and the voltage drop calculator shows the size of the gap before you commit the cable run.
For strips controlled by a PWM dimmer or driven from AC via a transformer, the AC sub-chain adds context: the impedance calculator and the reactance tools (capacitor, inductor) cover that territory.
Frequently Asked Questions
How long can a 12V LED strip run be before I need to inject power?
For a 14.4 W/m strip at 6 A, a single wire feed from one end becomes noticeably dimmer beyond about 5 m at 1.5 mm² wire or about 8 m at 2.5 mm². The solution is power injection: run a second pair of wires from the PSU to the midpoint or far end of the strip, connecting to the +12V and GND pads at that point. This halves the effective current per wire. For runs over 10 m, inject at both ends and the midpoint. Use the Wire Gauge Calculator with half the strip length as the run when injecting from both ends.
What goes wrong when you cut a strip between the marked cut points?
Each LED group on a strip shares one set of current-limiting resistors. Cut through the middle of a group and the resistors land on one piece while the LEDs land on the other: the resistor-side segment draws nothing; the LED-side segment has no current limiting and the LEDs burn out immediately on power-up. Cut only at the printed scissors symbols or copper-pad lines. After cutting, solder wires directly to the exposed pads or use snap-on strip connectors, and seal exposed copper with silicone if there is any chance of moisture.
What is the difference between 12V and 24V LED strips?
24V strips run at half the current for the same wattage, which means thinner wire, less voltage drop on long runs, and better dimming performance at low brightness levels. The trade-off is that 24V PSUs cost slightly more and 24V strips are slightly less common. For runs under 5 m and total power under 50W, 12V is simpler. For longer runs or higher-wattage installs, 24V is the better choice. Use the Watts / Volts / Amps Calculator to compare current at both voltages.
Do I need a resistor to run LED strips?
No, LED strips already have resistors built into each segment. Unlike individual LEDs, strips are designed to connect directly to the rated voltage (12V or 24V) with no external resistor. The resistors visible as small brown rectangular components on the strip PCB set the current for each LED group. For individual LEDs not on a strip, you do need a current-limiting resistor, use the LED Resistor Calculator for that.
Calculators used in this guide
Methodology and sources
This guide sizes a 12V or 24V LED strip circuit in four steps: total power and current, wire gauge for the run, fuse rating and (for mains installs) power-supply size. Every figure follows basic DC power physics plus the conventional continuous-load and voltage-drop margins used in low-voltage wiring.
- Method: Power (W) = strip rating (W/m) × length (m); Current (A) = power (W) / voltage (V), from P = V × I. Wire gauge is sized to keep voltage drop under 3% of the supply voltage. Fuse rating = normal current × 1.25 (the 125% continuous-load margin), rounded up to the next standard blade-fuse size. Mains PSU size = total power × 1.20, rounded up to a standard rating.
- Standards and sources: Standard DC power physics (Ohm's law, P = V × I) and conventional low-voltage wiring practice: the 3% voltage-drop guideline for lighting circuits, the 125% continuous-load rule (consistent with NEC Article 210.20 / 240.4 overcurrent sizing), and nearest-AWG to mm² conductor cross-references. No proprietary standard is implemented beyond these.
- Assumptions and limits: Copper conductors; one-way run length from supply to strip; a 3% voltage-drop target; and standard fuse increments (3, 5, 7.5, 10, 15 A). The AWG values shown are nearest-size approximations of the metric cross-sections, not exact equivalents. Real strips vary in actual W/m, and long runs may still need power injection. Ambient heat, conductor grouping and enclosure de-rating are not modelled here.
Reviewed and maintained by Rick Oosterling, who builds and wires 12 V, solar and EV systems hands-on. Last reviewed: June 2026. This guide is a planning aid, not a substitute for a qualified electrician or your local wiring and building code. Always confirm conductor ampacity, fuse placement and any mains connection against the applicable code before installing.