LED Strip Power Calculator
Estimate constant-voltage LED strip power, current, power-supply capacity, cable voltage drop, power-injection spacing, controller current and battery runtime.
Actual strip power depends on LED density, brightness, color mix, PWM duty, temperature, strip copper, manufacturing tolerance, controller efficiency, supply efficiency, cable length and conductor size.
Engineering tool
LED Strip Power Calculator
Estimate LED strip power, current, supply size, cable voltage drop, injection spacing, controller sizing, and battery runtime.
Common presets are 5 V, 12 V, 24 V, and 48 V.
Total installed LED strip length.
Use the strip datasheet value.
100% is worst-case full load.
Extra capacity above estimated load.
Dynamic Design Summary
5 m of 12 V LED strip at 14.4 W/m is about 72 W and 6 A. Recommended supply: at least 86.4 W / 7.2 A.
Result console
- Nominal strip power
- 72W
- Operating power
- 72W
- Total current
- 6A
- Recommended supply
- 86.4W
- Recommended current
- 7.2A
- Suggested supply size
- 100W
LED strip estimate is within the configured guidance thresholds.
Engineering Notes
- LED strip power density must come from the actual strip datasheet whenever possible.
Formula reference
LED Strip Power Formulas
Percent inputs are converted to decimal factors internally. Cable calculations model the supply and return path as a round trip.
Pnominal = L × PdensityPactual = Pnominal × FloadItotal = Pactual / VsPrecommended = Pactual × (1 + Fmargin)R = ρ × L / AVdrop = I × ReffectivePwire = I² × ReffectiveRuntime = usable battery Wh / operating powerVariable definitions
- L
- strip length
- Pdensity
- strip power per unit length
- Vs
- supply voltage
- ρ
- conductor resistivity
- A
- conductor cross-sectional area
- Fload, Fmargin
- decimal load and margin factors
Worked Examples
5 m × 14.4 W/m at 12 V gives 72 W nominal power, 6 A current, 86.4 W with 20% margin, and a practical 100 W supply suggestion.
300 addressable pixels at 60 mA each on 5 V can reach 18 A. With 1 W controller power, total system power is about 91 W.
A 5 A load over 5 m one-way 18 AWG copper wiring shows round-trip resistance, voltage drop, delivered voltage, cable loss and drop percentage.
A 10 m, 14.4 W/m strip at 12 V with 6 A feed limit needs about 2 segments, 1 injection point and 5 m per segment.
A 20 W strip on a 12 V, 10 Ah battery with 90% converter efficiency and 80% usable capacity gives about 86.4 Wh usable energy and 4.32 hours runtime.
Engineering Notes
- LED strips are usually rated by watts per meter or foot.
- Total current equals total power divided by strip voltage.
- Lower-voltage strips require more current for the same power.
- Long strips may require power injection.
- Feeding both ends can reduce voltage drop, but does not guarantee equal current sharing.
- Cable voltage drop and strip voltage drop are separate effects.
- RGB and RGBW maximum power usually occurs with several channels active.
- Addressable strips may have a high theoretical full-white current.
- A power supply should not be operated continuously at its absolute maximum rating.
- High-current DC systems require suitable fusing, connectors and wiring.
Common Mistakes
- Sizing the supply only by strip length without using watts per meter.
- Confusing amps with watts.
- Ignoring controller current limits.
- Ignoring voltage drop.
- Feeding a long strip from one end only.
- Forgetting that cable length is a round-trip electrical path.
- Applying no supply margin.
- Assuming addressable LEDs always consume maximum current.
- Using battery amp-hours without considering voltage.
- Ignoring converter efficiency in battery calculations.
Support reference
FAQ
How do I calculate LED strip power?
Multiply strip length by the strip watts-per-meter or watts-per-foot rating, then apply the expected brightness or load factor.
How large should the power supply be?
Use the estimated operating power plus design margin. A 20% margin is a common starting point, then choose the next practical supply rating.
How much power-supply margin should I use?
Many LED strip designs use at least 20% margin, but thermal conditions, enclosure rating, startup behavior, and continuous duty may require more.
Why are 5 V strips more sensitive to voltage drop?
The same absolute voltage drop is a larger percentage of a 5 V rail, and low voltage strips require more current for the same power.
When does an LED strip need power injection?
Power injection is often needed when strip length, current, or voltage drop would make the far end dimmer or under-voltage.
Should I feed an LED strip from both ends?
Feeding both ends can reduce voltage drop, but current sharing depends on strip copper resistance, cable resistance, connectors, and injection topology.
How do I calculate current from watts?
Divide power by strip voltage: I = P / V.
How much current does an addressable LED strip use?
Use the datasheet current per pixel. A 60 mA RGB pixel estimate is a common full-white worst-case value, but animations often consume less.
How do I size an RGB controller?
Check both total controller current and per-channel current, then add safety margin for the expected color mix and PWM duty.
How do I choose wire size for an LED strip?
Estimate current, one-way cable length, conductor material, and allowed voltage drop, then select a conductor with adequate area and thermal margin.
Does strip brightness affect power consumption?
Yes. PWM brightness, color mix, and active channel count reduce average power below full-white worst case.
How accurate is the battery-runtime estimate?
Runtime is approximate because battery voltage, usable capacity, converter efficiency, temperature, and discharge rate vary during operation.
Documentation
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Design notes, guides, and engineering articles linked to this tool.
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Disclaimer
This calculator provides engineering estimates and does not replace local electrical codes, qualified engineering review, datasheet limits, thermal testing, fusing analysis or installation safety requirements.