Calculator Form
Choose one calculation method. The result appears above this form after submission.
Example Data Table
| Method | Input Set | Key Formula | Example Result |
|---|---|---|---|
| Ohm's Law | 230 V, 10 A | R = V / I | 23 Ω |
| Resistivity | ρ = 1.724e-8 Ω·m, L = 30 m, A = 2.5 mm² | R = ρL / A | 0.20688 Ω |
| Temperature Correction | R₀ = 10 Ω, α = 0.00393, 20 °C to 80 °C | R = R₀[1 + α(T - T₀)] | 12.358 Ω |
| Parallel Network | 10 Ω, 20 Ω, 30 Ω | 1 / Req = Σ(1 / R) | 5.4545 Ω |
Formula Used
Ohm's Law
R = V / I
Resistance equals voltage divided by current. Use this when voltage and current are known for the same electrical path.
Resistivity Method
R = ρL / A
Resistance depends on material resistivity, conductor length, and cross-sectional area. Longer conductors increase resistance. Larger area reduces resistance.
Temperature Correction
R = R₀[1 + α(T - T₀)]
This linear model estimates resistance change with temperature. It works well for many conductors over moderate operating ranges.
Series Network
Req = R₁ + R₂ + ... + Rn
In series, all resistor values add directly because the same current flows through every resistor in the path.
Parallel Network
1 / Req = 1 / R₁ + 1 / R₂ + ... + 1 / Rn
In parallel, conductance adds. Equivalent resistance always becomes smaller than the smallest positive resistor in the set.
Useful Derived Value
G = 1 / R
Conductance is the reciprocal of resistance. It is measured in siemens and is useful for parallel-path analysis.
How to Use This Calculator
- Select the calculation method that matches your engineering problem.
- Enter values and choose the correct units for every input field.
- Use a material preset when you want quick approximate resistivity and temperature coefficient values.
- Click Calculate Resistance to show the result above the form.
- Review the output cards for resistance, conductance, and method-specific engineering details.
- Use the CSV or PDF buttons to save the current result for reports or documentation.
Frequently Asked Questions
1. What does this calculator measure?
It calculates electrical resistance using four methods: voltage-current, resistivity geometry, temperature correction, and resistor network equivalence.
2. When should I use the resistivity method?
Use it when you know the conductor material, length, and cross-sectional area, but do not have direct circuit voltage and current measurements.
3. Why does temperature change resistance?
Most conductive materials change electron scattering with temperature. For many metals, higher temperature increases resistance and lowers conductance.
4. Is the temperature model exact?
No. It is a practical linear approximation. It works well across moderate ranges, but extreme temperatures may need material-specific nonlinear data.
5. What is the difference between series and parallel resistance?
Series resistors add directly. Parallel resistors reduce the equivalent value because current has multiple available paths.
6. Can I enter resistor values in kilo-ohms or mega-ohms?
Yes. The network section supports mΩ, Ω, kΩ, and MΩ. The calculator converts them internally to ohms for accuracy.
7. Why is my parallel result smaller than every resistor?
That is normal. Parallel connections increase total conductance, so equivalent resistance becomes lower than the smallest positive branch resistance.
8. Can I use this for report preparation?
Yes. After calculation, download the result as CSV or PDF to support engineering notes, calculations, and project documentation.