Calculator Inputs
Choose a mode, define material behavior, and calculate surface resistance, required thickness, or high-frequency loss behavior.
Example Data Table
These sample cases show how surface resistance changes with conductivity, thickness, and frequency.
| Case | Material | Method | Input Snapshot | Surface Resistance |
|---|---|---|---|---|
| 1 | Copper foil | Sheet resistance | σ = 58 MS/m, t = 35 µm | 0.493 mΩ/sq |
| 2 | Copper conductor | Skin effect | σ = 58 MS/m, f = 1 MHz, μr = 1 | 0.261 mΩ/sq |
| 3 | Aluminum film | Sheet resistance | σ = 35 MS/m, t = 20 µm | 1.429 mΩ/sq |
| 4 | ITO coating | Sheet resistance | σ = 0.2 MS/m, t = 150 nm | 33.333 Ω/sq |
Formula Used
1) Sheet resistance from thickness
Rₛ = ρ(T) / t = 1 / (σ(T) · t)
Use this for thin films, coatings, traces, and planar conductors where thickness is known.
2) High-frequency surface resistance
Rₛ = √(π f μ / σ(T))
δ = √(1 / (π f μ σ(T)))
Use this when current crowds near the conductor surface because of skin effect.
3) Required thickness from target surface resistance
t = ρ(T) / Rₛ,target
This solves the thickness needed to achieve a chosen sheet-resistance limit.
4) Temperature correction
ρ(T) = ρref · [1 + α(T − Tref)]
The calculator adjusts conductivity and resistivity to the selected temperature before solving the main equation.
How to Use This Calculator
- Choose the calculation mode that matches your task.
- Select conductivity or resistivity as the input basis.
- Pick a material preset or enter custom material properties.
- Enter thickness, frequency, or target surface resistance as required.
- Set temperature, reference temperature, and temperature coefficient when thermal drift matters.
- Optionally enter path length and width to estimate actual strip resistance from squares.
- Press the calculate button and review the result table above the form.
Frequently Asked Questions
1. What is surface resistance?
Surface resistance expresses conductive loss per square area. It is usually written in ohms per square, making it useful for films, coatings, and distributed current paths.
2. Why is it called ohms per square?
For a uniform film, any perfect square has the same end-to-end resistance. Geometry only changes total resistance when the path contains multiple squares in series.
3. When should I use skin-effect mode?
Use skin-effect mode for higher frequencies where current flows near the conductor surface. It is common in RF conductors, microwave structures, and fast current transitions.
4. What is the difference between conductivity and resistivity?
Conductivity measures how easily current flows. Resistivity measures how strongly a material opposes current. They are reciprocals of each other, so either can drive the calculation.
5. Why does temperature matter?
Most metals become more resistive as temperature rises. That raises sheet resistance and surface loss. The calculator corrects the material property before computing the final result.
6. Can this estimate real trace resistance?
Yes. Enter optional path length and width. The calculator converts that geometry into squares, then multiplies by surface resistance to estimate end-to-end strip resistance.
7. What thickness should I compare against skin depth?
A thickness above about three skin depths usually supports the classic surface-resistance approximation well. Thinner conductors may carry current through more of the cross-section.
8. Is this calculator useful for coatings and transparent conductors?
Yes. It works well for plated surfaces, conductive inks, sputtered films, and transparent conductive coatings where sheet resistance is a practical design metric.