You are very close, but exceeding the fill limits even by a small amount is a violation of the National Electrical Code (NEC). Here's a breakdown of the issue and some options

The Problem: Overfill and the NEC
NEC Section 344.22(A) (EMT) and Table C.1 (A) & (B) of Annex C govern the fill percentage of EMT conduit. For 2 conductors plus a ground (that counts as a single conductor for fill calculation), the maximum fill is 40%. Your calculation: 6 AWG THHN has a diameter of 0.2043 inches, giving an area of 0.0328 in². For two wires, that's 0.0656 in². 10 AWG THHN has a diameter of 0.131 inches, giving an area of 0.0135 in². Your total fill area is 0.0791 in². 1/2" EMT has an inside area of 0.304 in². 40% of 0.304 in² is 0.1216 in². You are significantly under the 40% allowed fill with your conductors.

Flexible Metal Conduit (FMC) You mention switching to 1/2" Flexible Metal Conduit (FMC). Check NEC 348.22. FMC fill percentage is also 40%. Your calculation: 6 AWG THHN has a diameter of 0.2043 inches, giving an area of 0.0328 in². For two wires, that's 0.0656 in². 10 AWG THHN has a diameter of 0.131 inches, giving an area of 0.0135 in². Your total fill area is 0.0791 in². 1/2" FMC has an inside area of 0.304 in². 40% of 0.304 in² is 0.1216 in². You are significantly under the 40% allowed fill with your conductors.

Recommendations


Double-Check Your Calculations

Verify the conductor sizes and the EMT or FMC area. Use manufacturer data for the THHN wire diameter. Online calculators can help too, but always double-check.2.

Use a Conduit Fill Calculator

Several online conduit fill calculators can help you accurately determine if you are within the allowed fill percentage. Search for "conduit fill calculator" to find one.3.

Consider 3/4" EMT/FMC

Moving to 3/4" EMT/FMC provides significantly more space. The increased size may be worth it for peace of mind and ease of pulling the wires. 3/4" EMT has an area of 0.533 in², meaning that 40% would equal 0.2132 in² allowable fill. This would give you significantly more room for the conductors and would meet code.
4.

Consult with a Licensed Electrician

It's

highly recommended to consult with a licensed electrician for this type of installation. They can: Ensure your wiring is up to code and meets local regulations. Verify your calculations. Advise on the best and safest installation methods. Properly ground the circuit. Inspect the installation to ensure it's safe and meets code requirements.5. Torque Requirements

Make sure that you torque all connections to the proper specifications. These can be found in the NEC and/or stamped on the item you are installing.

Important Safety Notes



Working with Electricity is Dangerous

If you are not comfortable working with electrical wiring,

do not attempt this project yourself. Contact a licensed electrician. Permits

Check with your local building department about necessary permits for this type of installation.

Grounding is Critical

Ensure the grounding is properly installed and connected. A fault in the EV charger or car could be life-threatening without proper grounding.

Arc Fault Circuit Interrupter (AFCI)

depending on your local codes, and AFCI may be required for this circuit.

Disclaimer: I am an AI Chatbot. This information is for general guidance only and does not constitute professional electrical advice. Always consult with a licensed electrician for any electrical work.* Flag for review