What socket size are Honda spark plugs?
The typical spark plug socket size for Honda engines is 5/8 inch (16 mm).
In practice, most modern Honda cars and motorcycles use this size, but a few engines with larger plug hexes may require 13/16 inch (20.6 mm). Always verify for your exact model and plug type by checking the owner's manual or the plug packaging (NGK or Denso) for the hex size.
Common sizes used on Honda spark plugs
The following sizes cover the standard hex sizes you are likely to encounter when replacing Honda spark plugs. Use the one that matches your plug.
- 5/8 inch (16 mm) hex – standard for the majority of Honda spark plugs
- 13/16 inch (20.6 mm) hex – used on a minority of older or specific engines and specialty plugs
In most cases, the 5/8" socket will fit; if it does not, carefully check whether a larger 13/16" socket is required and ensure you have the correct plug type before forcing the tool.
Model-specific notes
There are occasional exceptions depending on the engine family or plug design. Always verify with the service manual for your exact model (for example, common 4-cylinder Honda engines and many motorcycles typically conform to the 5/8" size, while some older or high-performance engines might use the larger hex).
How to confirm the correct size for your Honda
Use these steps to determine the exact spark plug socket size for your vehicle.
- Check the owner’s manual or service manual for the recommended spark plug size and hex dimension for your engine.
- Inspect the spark plug packaging (NGK, Denso) if you are installing new plugs; the hex size is usually listed, or you can compare directly to a caliper.
- Place a 5/8 inch (16 mm) spark plug socket on the plug; if it slides on with a snug fit and no wobble, that is the correct size.
- If the 5/8" socket is loose or does not engage, try a 13/16" (20.6 mm) socket, and stop if it does not seat properly to avoid damaging the plug or threads.
- When in doubt, contact a Honda dealer or licensed mechanic to confirm the exact size for your model and year.
Always use a spark plug socket with a rubber insert to protect the plug and a torque wrench to avoid over-tightening.
Summary
For most Honda engines, a 5/8 inch (16 mm) spark plug socket is the standard size. Some older or special engines may require a larger 13/16 inch (20.6 mm) socket. To be sure, check your model’s manual or the plug packaging, and if needed, consult a dealership or mechanic. Using the correct size helps prevent cross-threading or damaging the plug and cylinder head.
