Free LED calculator
LED strip calculator: current, power supply and feed points
Enter strip type and length to get power, current per channel, feed points, power supply and feed cable instantly. No sign-up required.
Strip and feed cable
One-way distance; the return conductor is already included.
Power supply
100 W · 24 V
Required incl. reserve: 86.4 W
Calculation inputs
Voltage: 24 V DC
Colour channels: Single colour
Power per metre: 14.4 W/m
Strip length: 5 m
Max. length per feed: 5 m
Feed cable power supply → strip, one-way: 5 m
Power-supply reserve: 20 %
Max. feed-cable voltage drop: 3 %
Power
72 W
5 m
Current
3 A
Feed points
1
3 A per feed
Feed cable
0.75 mm²
ΔU 0.7 V · 2.92 %
Feed-cable cross-sections compared
| Cross-section | ΔU | Voltage at load | Max. feed-cable length |
|---|---|---|---|
| 0.5 mm² | 1.05 V · 4.38 % | 22.95 V | 3.4 m |
| 0.75 mm² | 0.7 V · 2.92 % | 23.3 V | 5.1 m |
| 1 mm² | 0.53 V · 2.19 % | 23.48 V | 6.9 m |
| 1.5 mm² | 0.35 V · 1.46 % | 23.65 V | 10.3 m |
| 2.5 mm² | 0.21 V · 0.88 % | 23.79 V | 17.1 m |
| 4 mm² | 0.13 V · 0.55 % | 23.87 V | 27.4 m |
| 6 mm² | 0.09 V · 0.36 % | 23.91 V | 41.1 m |
| 10 mm² | 0.05 V · 0.22 % | 23.95 V | 68.6 m |
Recommendation from 0.75 mm² (planning assumption). Check the current-carrying capacity of thin cables against the manufacturer's data.
Basis and limits
Planning values from datasheet data: power = W/m × length, current = power ÷ voltage, voltage drop with 0.0175 (copper) or 0.029 Ω·mm²/m (aluminium). Power-supply sizes are typical commercial ratings.
Datasheets confirm length per feed, derating, heat dissipation in the profile and the cable's current-carrying capacity. Protection and the AREI/RGIE rules for SELV, bathrooms and outdoor areas are planned and checked in the PlanElec project.
What does this calculator do?
Power per metre and length give total power and current. The manufacturer's maximum length per feed sets how often the strip must be fed. Adding the reserve gives the power-supply size. For the cable from the power supply to the strip, the calculator compares cross-sections and recommends the smallest one within the voltage-drop limit.
Frequently asked questions
Why does the power supply need a reserve?
A power supply running permanently at its rated power gets warm and ages faster. A 20% reserve is a common planning assumption. At high ambient temperature or in tight enclosures, the datasheet derating applies.
Why several feed points?
Voltage also drops along the strip itself. If it is too long, the end gets dimmer and multi-colour strips shift in colour. Manufacturers therefore state a maximum length per feed. Feed longer runs several times, each feed with its own cable to the power supply.
How are RGB, RGBW and CCT strips calculated?
Power per metre applies with all channels at full brightness and is split evenly across the channels. The common positive conductor carries the current of all channels, each channel conductor only its share; the voltage drop accounts for this. The controller must be able to supply the current per channel.
Do AREI/RGIE limits apply to the feed cable?
The AREI/RGIE gives no fixed percentage for the voltage drop of an extra-low-voltage feed cable. We design for 3% so the strip lights evenly. The manufacturer's datasheet confirms the current-carrying capacity of thin cables.
12 V, 24 V or 48 V?
At the same power, doubling the voltage halves the current. That reduces voltage drop and cross-section and allows longer runs per feed. 5 V is only suitable for short or digital strips. Bathrooms and outdoor areas are planned with the additional AREI/RGIE rules in the PlanElec project.