--- title: What Cable Size Should You Use in a 12V Automotive System? description: Learn how to choose the correct cable and fuse size for your car’s 12V components using current rating, cable type, and OHM’s law for safe, efficient wiring. --- [Skip to content](https://info.speedingparts.eu/what-cable-size-should-you-use-in-a-12v-automotive-system#main-content) [![Speeding\_Logo\_black\_Byline\_pp-2](https://info.speedingparts.eu/hs-fs/hubfs/Speeding_Logo_black_Byline_pp-2.png?width=200&height=60&name=Speeding_Logo_black_Byline_pp-2.png)](https://www.speedingparts.eu) Open main navigation Close main navigation How can we help you? - There are no suggestions because the search field is empty. 1. [Speeding Support](https://info.speedingparts.eu/?hsLang=en) 2. [Electrical](https://info.speedingparts.eu/electrical?hsLang=en) # What Cable Size Should You Use in a 12V Automotive System? ## Learn how to choose the correct cable and fuse size for your car’s 12V components using current rating, cable type, and OHM’s law for safe, efficient wiring. ### *Cable size* Which cable cable size should be used for different components / product? Here we go through how to do in the car's 12v system.   ![](https://www.speedingparts.com/image/15555/motorsport_wiring_cable.jpg)   ### *Check the product MAX current (Ampere)* Start by seeing what the product's MAX current (Ampere) is. Depending on which part / product is to be connected and how long cable you are going to use, you need to use the right cable size and then you need to know how much current the product use as MAX. The difference is large between a fan and a lamp e.g. Example: Bosch 044 fuel pump use approximately 13.5A at ~5bar back pressure. Here you can use a 1.5mm2 RK cable. Then you can secure with a 15Ampere fuse   ### *RK / RKUB cable size (mm2)* Cable area (mm2) - **Max current (A)** 0.5mm2 - **5A** 0.75mm2 - **7.5A** 1mm2 - **10A** 1.5mm2 - **15A** 2.5mm2 - **20A** 4mm2 - **30A** 6mm2 - **40A** 8mm2 - **50A** 10mm2 - **70A**   ### Cable area R2 / TXL (mm2) If you use finer cable such as R2 or TXL as an example, you can follow this table: Cable area (mm2) - **Max current (A)** 0.5mm2 - **10A** 1mm2 - **15A** 1.5mm2 - **20A** 2mm2 - **25A** 3mm2 - **30A** 4mm2 - **40A** 6mm2 - **50A** 8mm2 - **60A** 10mm2 - **70A**   ### *Fuse size* A fuse is used to protect cable and products connected to it. Use the same or smaller fuse as in the table above.   ### *Summary* To summarize this short guide in 3 steps: 1 - Check the product MAX current (Ampere) 2 - Check the size of cable you need (mm2) 3 - Secure by cable / consumer with suitable fuse     ### **Extra** - calculate yourself?     #### **OHM:s law** The cable sizing differs depending on the length you use, but in a car where a maximum of about 5 meters is used, the voltage drop in the cable is okay using the tables above. If you want to calculate the exact cable size for the products in your system, use OHM's law. ![](https://www.speedingparts.com/image/15554/ohms-lag-1.png)   - [Hose and Fittings](https://info.speedingparts.eu/hose-and-fittings?hsLang=en) - [Engine](https://info.speedingparts.eu/engine?hsLang=en) - [Fuel System](https://info.speedingparts.eu/fuel-system?hsLang=en) - [Brake system](https://info.speedingparts.eu/brake-system?hsLang=en) - [Chassis](https://info.speedingparts.eu/chassis?hsLang=en) - [Powertrain](https://info.speedingparts.eu/powertrain?hsLang=en) - [Electrical](https://info.speedingparts.eu/electrical?hsLang=en) - [Turbo](https://info.speedingparts.eu/turbo?hsLang=en) [![Speeding\_Logo\_black\_Byline\_pp-2](https://info.speedingparts.eu/hs-fs/hubfs/Speeding_Logo_black_Byline_pp-2.png?width=200&height=60&name=Speeding_Logo_black_Byline_pp-2.png "Speeding_Logo_black_Byline_pp-2")](https://www.speedingparts.eu) Copyright © 2026, Speeding AB