Free LED strip power supply calculator. Enter strip length, watts per foot, and voltage to get total wattage, a recommended PSU size with safety headroom, current draw, and a voltage-drop warning for long runs.
Use this before wiring up an LED strip lighting project — under-cabinet, accent, or architectural lighting — to size a power supply correctly and catch long runs that will suffer visible voltage drop before you've mounted anything.
Compared to just reading a strip's wattage-per-meter spec sheet, this calculator bakes in the safety headroom convention, snaps the result to real off-the-shelf PSU sizes, and flags voltage-drop risk based on run length and voltage — three things a raw wattage number alone won't tell you.
Total wattage is strip length × watts per foot × number of parallel runs sharing one power supply.
The required PSU rating adds your safety headroom percentage on top of that load, then the calculator picks the smallest standard PSU size (12–350W) that still covers it.
Current draw (amps) divides total watts by voltage, and a voltage-drop warning triggers when a single run exceeds roughly 16 ft at 12V or 32 ft at 24V — the point where injecting power at both ends becomes worthwhile.
Continuous full-load operation shortens a PSU's lifespan and increases heat, which is why this calculator adds a safety headroom (default 20%) on top of the strip's actual power draw before recommending a size.
Voltage drop becomes noticeable on runs longer than about 16 feet at 12V or 32 feet at 24V, showing up as dimming or color shift toward the far end. Feeding power in at both ends of the run (power injection) evens out the voltage along the strip.
24V strips carry the same power at half the current of 12V, which cuts voltage drop roughly in half and lets you run longer single runs before needing power injection. For runs beyond about 16 feet, 24V is usually the better choice.
The calculator takes your total wattage, adds the safety headroom percentage, and picks the smallest common PSU size (12, 20, 30, 60, 100, 150, 200, or 350W) that still covers the padded load.
입력
16.4 ft strip (one 5m reel), 4.8 W/ft, 12V, 20% headroom, 1 run.
출력
Total load 78.7W; recommended 100W PSU; 6.56A draw; run exceeds 16 ft — power injection recommended.
A 16.4 ft, 4.8 W/ft strip draws 78.72W; padding by 20% headroom requires 94.46W of PSU capacity, so the calculator recommends the next standard size up, a 100W supply, drawing 6.56A at 12V. Because the run is just over the 16 ft threshold for 12V, power injection at both ends is suggested.