Artificial Intelligence Response
Direct answer to the question
There is no single standard diameter for coaxial cable.
“Coaxial cable” is a family of cables, not one fixed size. The diameter depends on the cable type, impedance, shielding, and intended application.
Common nominal outer diameters:
- RG-58: about 4.95 mm (\(0.195"\))
- RG-59: about 6.15 mm (\(0.242"\))
- RG-6: about 6.7 to 7.0 mm (\(0.265" \text{ to } 0.275"\))
- RG-11: about 10.3 mm (\(0.405"\))
If you mean the usual household TV / cable / satellite coax, the practical “standard” is usually RG-6, about 6.8 mm OD.
Detailed problem analysis
The question is slightly ambiguous because “standard diameter” can mean different things:
-
A universal standard for all coaxial cable
- This does not exist.
- Coax is made in many diameters, from very small micro-coax used inside electronics to large hardline used in telecom infrastructure.
-
The most common domestic coax size
- In residential installations, the most common cable is RG-6.
- Its outer diameter is typically around 6.8 mm.
-
A dimension needed for connectors or routing holes
- In practice, you should not specify coax by diameter alone.
- You should specify:
- cable type: RG-6, RG-58, RG-11, etc.
- impedance: usually 50 \(\Omega\) or 75 \(\Omega\)
- shielding style: standard, dual shield, quad shield
- jacket type: PVC, PE, plenum, etc.
Why there is no single diameter
The geometry of a coaxial cable is chosen to achieve a target characteristic impedance and performance. The impedance depends on the ratio between conductor diameter and the inner diameter of the shield, together with dielectric constant:
\[
Z_0 \approx \frac{60}{\sqrt{\varepsilon_r}} \ln\left(\frac{D}{d}\right)
\]
Where:
- \(Z_0\) = characteristic impedance
- \(D\) = inner diameter of outer conductor
- \(d\) = diameter of center conductor
- \(\varepsilon_r\) = relative permittivity of dielectric
So the diameter is a result of the electrical design, not a universal standard.
Typical examples
| Cable type |
Typical impedance |
Approx. outer diameter |
Typical use |
| RG-58 |
50 \(\Omega\) |
4.95 mm |
RF patch leads, lab use |
| RG-59 |
75 \(\Omega\) |
6.15 mm |
Legacy video, CCTV |
| RG-6 |
75 \(\Omega\) |
6.7–7.0 mm |
TV, cable modem, satellite |
| RG-11 |
75 \(\Omega\) |
10.3 mm |
Longer CATV runs |
| RG-8 / LMR-400 class |
50 \(\Omega\) |
10.3 mm |
Lower-loss RF feedlines |
Important engineering point
Two coaxial cables can have similar outer diameters but different electrical properties.
Therefore, for design or installation, diameter alone is not enough.
Current information and trends
For modern general-purpose use:
- RG-6 is the de facto standard in residential TV/broadband/satellite systems.
- RG-59 is now mostly older or specialized legacy video/CCTV cable.
- Larger low-loss coax remains common in RF infrastructure where attenuation matters.
- Micro-coax is widely used internally in laptops, phones, routers, and compact RF modules.
A relevant modern trend is that the phrase “standard coax” often depends on context:
- consumer AV / CATV → usually RG-6
- general RF bench/lab → often RG-58
- low-loss outdoor RF links → often LMR-400 class
Supporting explanations and details
Think of coax diameter like wire gauge in power wiring: there is no single standard size for all jobs.
The outer diameter changes because of:
- shield thickness
- number of shields
- for example, quad-shield RG-6 is slightly thicker than standard RG-6
- dielectric material
- center conductor size
- jacket material and environmental rating
Practical implication
If you are buying:
- connectors
- compression fittings
- strain relief
- glands
- cable clamps
- feedthroughs
you must match the exact cable family, not just “coax”.
For example:
- an RG-59 connector is not the same as an RG-6 connector
- even within RG-6, some connectors are sized differently for standard vs quad-shield cable
Ethical and legal aspects
This topic has limited ethical content, but some practical compliance aspects matter:
- Use the correct cable type for signal integrity and safety
- In buildings, use the proper jacket rating where required:
- plenum-rated
- riser-rated
- outdoor UV-resistant
- In communications systems, improper cable substitution can cause:
- excessive attenuation
- EMC issues
- poor shielding
- regulatory non-compliance in some installations
Practical guidelines
Best way to specify coax
Use this format:
- Type: RG-6 / RG-58 / RG-11 / LMR-400
- Impedance: 50 \(\Omega\) or 75 \(\Omega\)
- Outer diameter: nominal value
- Shielding: standard / dual / quad
- Application: TV / RF / instrumentation / telecom
If you need to identify a cable
- Read the printing on the jacket.
- Measure the outer diameter with calipers.
- Confirm the impedance and connector family.
- Check whether it is standard-shield or quad-shield.
Quick rule of thumb
- If it is home TV coax, assume RG-6, about 6.8 mm
- If it is thin RF test cable, often RG-58, about 5 mm
- If it is thick low-loss cable, often around 10 mm or more
Possible disclaimers or additional notes
- Published diameters are usually nominal, not exact.
- Different manufacturers may vary slightly.
- “RG” designations are widely used, but commercial products can differ in construction.
- Outer diameter does not uniquely determine impedance or loss.
Suggestions for further research
If your real goal is practical selection, the next useful question is usually one of these:
- What coax diameter fits a certain connector?
- Which coax should I use for TV, Wi-Fi, SDR, ham radio, or CCTV?
- What is the difference between 50 \(\Omega\) and 75 \(\Omega\) coax?
- How much signal loss occurs per meter for a given cable type?
Brief summary
There is no universal standard diameter for coaxial cable.
The diameter depends on the cable family and application.
The most common examples are:
- RG-58: ~4.95 mm
- RG-59: ~6.15 mm
- RG-6: ~6.8 mm
- RG-11: ~10.3 mm
If by “standard coax” you mean the typical household TV cable, the answer is usually RG-6, about 6.8 mm outer diameter.
If you want, I can also give you a one-line answer for connectors/installers, or a table of coax sizes by application.
