Is 12V Sim really free?

Yes. Completely free - no ads, no account, no subscription, and no registration. Open app.12vsim.com and start wiring.

Does it work as a wire gauge calculator for 12V?

Yes. Every wire has AWG or mm2 and length. The simulator checks ampacity and shows live current - it replaces a separate wire gauge calculator 12v or wire gauge calculator dc for schematic work.

Can I check voltage drop?

Run the sim to see live voltage at every node. Design Review includes a voltage drop category so you catch excessive drop across long or undersized runs.

Is this an online circuit simulator?

12V Sim is a browser-based online circuit simulator focused on 12V DC and low-voltage wiring - boats, RVs, campers, cars, and off-grid installs.

Can it help with automotive or car electrical repair?

12V Sim is a design and test tool, not a repair manual. Use it to plan car electrical wiring or vehicle electrical work before you cut wire - validate fuses, relays, and loads so automotive electrical repair goes faster with fewer surprises.

What about auto electrical repair or truck wiring?

Same idea: build the circuit, run the dc circuit simulator, fix design issues first. That reduces guesswork during auto electrical repair and helps you understand the system you are fixing.

Do I need to install anything?

No. It runs in Chrome, Firefox, Safari, or Edge. Designs save to your browser LocalStorage unless you export JSON.

12V Sim - Free 12V DC Wiring Simulator

Free online circuit simulator with wire gauge calculator, voltage drop analysis, and wiring diagrams. No ads, no account, no registration.

Wire calculators built in

Wire size calculator, wire gauge calculator 12v, dc wire size calculator, and voltage drop calculator - all inside the simulator on every cable run.

Wiring diagrams

Build and simulate a 12v wiring diagram, boat wiring diagram, rv electrical wiring diagram, battery wiring diagram, relay wiring diagram, 12 volt relay wiring diagram, or off grid solar wiring diagram.

Systems

Plan a camper van electrical system, rv electrical system, off grid electrical system, car electrical wiring, and low voltage wiring with live DC simulation.

Launch the free simulator at app.12vsim.com