Resistivity Calculator
Calculate electrical resistivity, conductivity, and resistance with precision
What is Electrical Resistivity?
Electrical resistivity (symbol: ρ) is a fundamental property of materials that measures how strongly a material opposes the flow of electric current. Unlike resistance, which depends on the size and shape of a conductor, resistivity is an intrinsic property of the material itself.
The SI unit of resistivity is the ohm-meter (Ω·m). Materials with low resistivity (like copper and silver) are good conductors, while materials with high resistivity (like rubber and glass) are insulators. For a deeper understanding of this topic, you can read about electrical resistivity and conductivity.
Resistivity and Conductivity
Electrical conductivity (symbol: σ) is the inverse of resistivity. It measures how easily electric current flows through a material.
The SI unit of conductivity is siemens per meter (S/m).
Quick Comparison
- High resistivity, low conductivity = Insulator (e.g., rubber, glass)
- Low resistivity, high conductivity = Good conductor (e.g., copper, silver)
- Medium resistivity = Semiconductor (e.g., silicon, germanium)
Common Material Resistivity Values
Here are the resistivity values for common materials at 20°C (room temperature):
| Material | Resistivity (Ω·m) | Conductivity (S/m) | Type |
|---|---|---|---|
| Silver | 1.59 × 10⁻⁸ | 6.30 × 10⁷ | Conductor |
| Copper | 1.68 × 10⁻⁸ | 5.96 × 10⁷ | Conductor |
| Gold | 2.44 × 10⁻⁸ | 4.10 × 10⁷ | Conductor |
| Aluminum | 2.65 × 10⁻⁸ | 3.77 × 10⁷ | Conductor |
| Tungsten | 5.60 × 10⁻⁸ | 1.79 × 10⁷ | Conductor |
| Iron | 9.71 × 10⁻⁸ | 1.03 × 10⁷ | Conductor |
| Nichrome | 1.10 × 10⁻⁶ | 9.09 × 10⁵ | Alloy |
| Silicon | 6.40 × 10² | 1.56 × 10⁻³ | Semiconductor |
For more material properties and detailed information, you can explore our Ohm’s Law Calculator and Ohms to Watts Calculator.
Step-by-Step Calculation Example
Example: Find the resistivity of a wire
A wire has a resistance of 0.214 Ω, length of 10 meters, and diameter of 1 mm. What is the resistivity of this wire?
Step 1: Calculate cross-sectional area (circular wire)
Diameter = 1 mm = 0.001 m
Radius = 0.0005 m
A = π × r² = π × (0.0005)² = 7.854 × 10⁻⁷ m²
Step 2: Apply the resistivity formula
ρ = R × (A / L)
ρ = 0.214 × (7.854 × 10⁻⁷ / 10)
ρ = 0.214 × 7.854 × 10⁻⁸
Result:
ρ = 1.68 × 10⁻⁸ Ω·m (This matches copper’s standard resistivity!)
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Important Notes
Key Considerations
- Wire gauge: For circular wires, you can calculate area from diameter using A = π × (d/2)²
- Unit consistency: Ensure all measurements are in compatible units (SI units recommended)
- Material purity: Impurities in materials can significantly affect resistivity
- Alloys: Alloys like nichrome have higher resistivity than pure metals