Calculate and convert cable cross-section
Convert diameter to cross-sectional area or calculate voltage drop. The geometric conversion applies to solid, round conductors. For stranded copper conductors, use the nominal cross-section stated on the cable or datasheet. These results are a guide to cable selection.
Jetzt berechnenQuick Calculator
Quickly convert diameter and cross-section
Diameter ↔ cross-section
Convert the diameter in mm and area in mm² of a round conductor
Suggested cross-section
nächstgrößerer verfügbarer Standard-Querschnitt
Why choose the next larger cross-section?
- More safety margin — less risk of overload
- Lower voltage drop — better performance over longer cable runs
- Less heat build-up — longer service life
- Allowance for future needs — reserve for future increases in power
Cross-section ↔ diameter: geometric circular area of a solid, round conductor
Geometric reference values. This table does not determine the nominal cross-section of a fine-stranded conductor.
| Cross-section mm² | Approx. diameter mm |
|---|---|
| 1,5 | 1,38 |
| 2,5 | 1,78 |
| 4 | 2,26 |
| 6 | 2,76 |
| 10 | 3,57 |
| 16 | 4,51 |
| 25 | 5,64 |
| 35 | 6,68 |
| 50 | 7,98 |
| 70 | 9,44 |
| 95 | 11,00 |
| 120 | 12,36 |
| 150 | 13,82 |
Calculate a minimum cross-section from cable length, current and voltage?
Jetzt Querschnitt berechnenUndersized cables can overheat and pose a fire risk
Diameter ≠ cross-section — mm² is what matters
A poor choice costs time and money
Why mm² matters more than diameter
The cross-section in mm² is the actual area of conductor carrying current. A larger cross-section provides greater conductance and lower resistance.
For a solid, round conductor, the geometric area can be calculated from its diameter: A = (d² / 4) × π. When choosing a stranded cable, use the nominal cross-section stated on the cable or datasheet.
Remember: Doubling the diameter quadruples the cross-sectional area. This is why the mm² value matters when sizing a cable.
= 4× Querschnitt
Calculating and converting cable cross-section
Correct cable sizing is a basic requirement for electrical installations. An undersized cable can heat up under load, cause power losses or, in the worst case, start a fire.
From diameter to cross-section
Use the formula A = (d² / 4) × π to convert the diameter of a solid, round conductor into its geometric area. The bundle diameter of fine-stranded copper is not suitable for this conversion. Find the nominal cross-section on the cable or datasheet. If it is missing, we can help identify the cable.
Calculate minimum cross-section
Our calculator helps with initial selection. Current, cable length and voltage are important inputs. Final selection must also account for installation method, ambient temperature, protective devices and permissible voltage drop. The applicable requirements, including DIN VDE 0298-4 or DIN 18015-1, depend on the installation. A general percentage limit alone is not sufficient for complete cable sizing.
Safety guidance
Our calculators help with initial selection. A qualified electrician must check final sizing for the specific installation. A larger cross-section alone does not confirm that the protective device or installation method is suitable. Contact us for advice on your application.
Frequently asked questions about the cable calculator
The diameter is specified in mm, the cross-section in mm². For a solid, circular conductor, the geometric formula A = π × d² / 4 applies. For a stranded wire, the diameter of the entire wire bundle must not be treated as a solid conductor. Use the specified nominal cross-section for cable selection.
If you would like to measure the cable cross-section, first check the cable imprint or the data sheet, for example, the specification H07V-K 16 mm². Measuring the diameter of the strand bundle with a caliper does not reliably determine the nominal cross-section. The geometric conversion using the circle formula applies to a solid, circular conductor. The sheath and insulation are not part of the conductor area.
Common nominal cross-sections are 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185 and 240 mm². Depending on the cable type, other sizes are available. The calculator is based on the stored standard sizes. You can see which versions are available for order on the respective cable page.
If the result falls between two sizes stored in the calculator, the next largest size is displayed. This makes it easier to compare with the product range. The selection must also be compatible with the current-carrying capacity, the permissible voltage drop, the fuse protection, and the installation method.
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