LED Strip PCB Current Calculator
Copper Sizing | Power Injection | Flex and Rigid LED Boards
Use this page to choose a defensible starting point for LED strip PCB current sizing: how much current the entry copper really carries, when to add power injection, and when a lighting layout needs wider copper, heavier copper, or a different strip voltage instead of one more marginal trace tweak.
For LED strip boards, size copper at the power-entry end for the total downstream load, not for one LED segment. A 12 V strip rated at 14.4 W/m draws about 1.2 A per meter, while a 24 V strip at 19.2 W/m draws about 0.8 A per meter. If several meters are fed from one end, the first copper section carries the sum of every downstream meter, which is why many strips need wider feed copper, copper pours, or power injection long before the LED pads themselves look stressed.
Key Takeaways
- •The hottest copper on an LED strip is usually the first section after the power connector because current accumulates toward the feed point.
- •Use the simple rule I = P / V to estimate strip current, then calculate the worst-case current in each copper section rather than only the average current per meter.
- •Flexible LED strips have less thermal mass and usually justify shorter power-injection intervals than rigid FR4 lighting boards.
- •If the strip changes layers, uses stitched copper islands, or fans through narrow connector pads, verify those vias and neck-downs explicitly.
LED Strip Current per Meter Cheat Sheet
| Strip Type | Current per Meter | Feed-Point Example | PCB Implication |
|---|---|---|---|
| 12 V analog strip, 4.8 W/m | ~0.40 A/m | 5 m from one end = ~2.0 A | Usually manageable on short runs, but check connector pads and narrow feed tails. |
| 12 V analog strip, 9.6 W/m | ~0.80 A/m | 5 m from one end = ~4.0 A | A single-end feed can heat the first copper section quickly on flex strips. |
| 12 V analog strip, 14.4 W/m | ~1.20 A/m | 5 m from one end = ~6.0 A | Strong candidate for mid-span injection or a heavier entry copper region. |
| 24 V analog strip, 19.2 W/m | ~0.80 A/m | 5 m from one end = ~4.0 A | 24 V reduces current per meter, which usually improves copper loss and brightness uniformity. |
| 5 V addressable strip, 60 px/m full-white worst case | ~3.6 A/m | 2 m from one end = ~7.2 A | Very aggressive for narrow flex copper; frequent power injection is usually mandatory. |
These are practical worst-case planning numbers. Actual average current may be lower, but entry copper, connector pads, and thermal bottlenecks should be reviewed against worst-case full-brightness load.
Which Part of the Strip Should You Calculate?
| PCB Zone | Current Profile | What to Calculate | Recommendation | Common Mistake |
|---|---|---|---|---|
| Power connector to first LED section | Highest cumulative current on the strip | Trace width, temperature rise, connector pad neck-down | Use the main trace width calculator with worst-case downstream current and consider local copper widening or pours. | Sizing this section from one segment current instead of total strip current. |
| Intermediate strip section | Current falls as load is distributed | Voltage drop and brightness consistency | Estimate current meter by meter and add power injection before visible dimming or color shift shows up. | Assuming every section needs the same width as the entry copper. |
| Layer change or stitched copper jumper | Localized thermal bottleneck | Via current, via count, and copper spreading | Use multiple vias or parallel transitions wherever the main feed changes layers. | Making the top trace wide but forcing all current through one small via. |
| LED pad neck-down and resistor islands | Short local current with concentrated heating | Neck-down width, thermal relief, and manufacturability | Review the narrowest copper feature, not only the wide trunk trace. | Ignoring short narrow sections because they look electrically insignificant. |
Practical LED Strip PCB Workflow
Use strip rating and bus voltage to compute worst-case current with I = P / V for each meter or panel section.
LED strip copper must be sized from cumulative downstream current, especially at the entry end.
Open Current Capacity Calculator →Use the widest downstream current section in the main trace width calculator, then check whether the design still fits your process limits.
This tells you whether 1 oz copper, a wider trace, or a copper pour is the right starting point.
Open Trace Width Calculator →Decide whether the strip is rigid FR4 or flexible polyimide and adjust thermal expectations accordingly.
Flex strips run hotter for the same copper geometry, so the safe injection interval is often shorter.
Open Flex PCB Calculator →Check connector pads, stitched copper, thermal-relief choices, and any layer transitions in the power path.
LED strip failures usually start at narrow features, via bottlenecks, or connector launch regions.
Open Via Current Calculator →Decision Rules That Save Rework
- •Calculate current at the strip entry from the full downstream length, not from one cut segment.
- •Treat brightness drop and copper heating as the same design problem because both are driven by distributed IR loss.
- •Prefer 24 V strips over 12 V when the same optical power must travel farther on the PCB copper.
- •Schedule power injection wherever the entry section becomes too wide, too hot, or causes visible color shift.
- •Inspect connector pads, test pads, solder jumpers, and fused sections for hidden neck-downs.
- •If the strip is flexible, use more conservative temperature-rise assumptions than you would for a rigid FR4 lighting board.
Recommended Supporting Calculators
LED Strip PCB Current FAQ
How do I calculate current for an LED strip PCB?
Start with I = P / V. A 12 V strip rated at 14.4 W/m draws about 1.2 A per meter, and a 24 V strip rated at 19.2 W/m draws about 0.8 A per meter. The critical step is then summing the downstream load in each copper section, because the first section after the power input carries the most current.
Why do LED strips need power injection even when the copper looks wide enough?
Power injection is often driven by voltage drop and thermal margin together. Even if the copper survives thermally, a long strip can still dim or shift color because the bus voltage sags as current flows through the distributed copper resistance.
Is 24 V better than 12 V for long LED strip PCBs?
For the same power level, 24 V cuts current roughly in half compared with 12 V. That usually reduces voltage drop, entry-trace heating, and the number of injection points needed. The tradeoff is compatibility with the LED segment architecture and driver choice.
What part of an LED strip PCB usually overheats first?
The most common hot spots are the power-entry copper, connector pads, fuse sections, and any short neck-down or layer transition near the feed point. Those sections can run hotter than the rest of the strip because they carry the combined load of multiple downstream LEDs.
Size the Copper Before You Commit the Strip Layout
Run the high-current entry sections through the calculator first, then decide whether the right answer is a wider trace, heavier copper, a shorter feed length, or an extra power-injection point.
Related Tools & Resources
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Flex PCB Calculator
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