Calculation of cable cross-section
Determination of the area of a conductor by its diameter
to instantly calculate the cross-section
Calculation of cable cross-section by diameter: online calculator and GOST table
⚡ How to determine the cable cross-section by diameter
Our tool helps to accurately determine the cross-sectional area of the core, knowing its diameter. This is critical for safety: if you choose a cable that is too thin, it will start to heat up, which can lead to the insulation melting and a fire. The calculations comply with the rules PUE.
Table: correspondence of diameter and cross-section (Copper, GOST)
For a quick check of standard copper strands, use this chart. If your measurements differ, use the calculator above.
| Section (mm²) | Diameter Ø (mm) | Current (A) |
|---|---|---|
| 0.75 | 0.98 | 15 |
| 1.0 | 1.13 | 17 |
| 1.5 | 1.38 | 23 |
| 2.5 | 1.78 | 30 |
| 4.0 | 2.26 | 41 |
| 6.0 | 2.76 | 50 |
| 10.0 | 3.57 | 80 |
🛠 Life hack: How to measure the diameter without a caliper?
If you only have a ruler at hand, use the “pencil method”. It gives high accuracy even with a regular school ruler.
- Strip the wire from insulation (20–30 centimeters).
- Wrap the wire tightly around a pencil, screwdriver or pen. Make exactly 10 turns (the turns should be pressed against each other).
- Measure the total length of the winding in millimeters with a ruler.
- Divide the resulting length by 10.
Example: 10 turns took 18 mm. This means the diameter of the core: 18 / 10 = 1.8 mm.
Calculation formulas
For those who want to check the calculations manually:
- S – cross-sectional area (mm²)
- d—core diameter (mm)
- π - Pi number (3.1415)
For single-core cable:
S = (π d²) / 4 or simplified: S = 0.785 · d²
For stranded (soft) wire:
S = 0.785 d² N 0.8
where N is the number of veins in the bundle, and 0.8 is the air gap coefficient.
After calculating the cross-section, be sure to check whether your circuit breaker is suitable for this cable. Use our machine selection calculator to prevent line overheating.
Frequently asked questions (FAQ)
❓ Can you trust the markings on the cable?
Unfortunately, not always. Many manufacturers produce cables according to specifications (technical specifications), and not according to GOST, lowering the cross-section by 10-15% to save copper. Checking the diameter is the only reliable way to find out the truth.
❓ What is the actual diameter of a 2.5 mm² cable?
An honest cable with a cross-section of 2.5 mm² (GOST) should have a core diameter of 1.78 mm. If you measure 1.5-1.6 mm, this is a trimmed section that will withstand less load.
❓ How to check an aluminum cable?
The formula for calculating the cross-sectional area for aluminum is the same as for copper. However, remember: aluminum conducts current less well, so a larger cable cross-section is required for the same load.
❓ What to do if the cross-section is smaller than stated?
If instead of 2.5 mm² you find 1.8 mm², such a cable cannot be installed on power sockets. Use it only for lighting or low-power applications, or return it to the seller.