Dielectric Constant Calculator

About the Dielectric Constant Calculator

The Dielectric Constant Calculator determines capacitance, electric field, stored energy, and breakdown voltage for parallel plate capacitors with various dielectric materials. The dielectric constant (relative permittivity, κ or εᵣ) describes how much a material increases capacitance compared to vacuum.

A parallel plate capacitor with a dielectric has capacitance C = κ × ε₀ × A / d, where κ is the dielectric constant, ε₀ is vacuum permittivity (8.854 × 10⁻¹² F/m), A is plate area, and d is plate separation. Higher κ means more capacitance. But dielectric strength (breakdown voltage per mm) limits the maximum voltage — exceeding it destroys the dielectric.

Select from 40+ common materials (air, FR-4, polyethylene, ceramic, mica, water) or enter a custom dielectric constant to calculate capacitor parameters and compare materials. It gives you a fast way to compare materials before you commit to a design. That is useful when you want a material check without manual lookup tables.

When This Page Helps

Use this calculator when you want to compare dielectric materials by capacitance and breakdown behavior instead of looking only at the material name. It is useful for capacitor selection, PCB work, and insulation checks where thickness and field strength matter together. That makes it easier to see both storage and safety limits at once.

How to Use the Inputs

1. Select a dielectric material from the database, or enter a custom κ value.
2. Enter the plate area in cm² or mm².
3. Enter the dielectric thickness (plate separation) in mm.
4. Review capacitance, electric field, stored energy, and breakdown margins.
5. Compare materials using the reference table below.
6. Use the thickness optimization table to explore design trade-offs.

Example Calculation

Tips & Best Practices

• Dielectric constant decreases at higher frequencies for most materials — use RF-frequency values for high-speed designs.
• Multi-layer ceramic capacitors (MLCCs) use very thin layers (1-10 µm) to maximize C/volume.
• Doubling the plate area doubles capacitance; halving thickness doubles capacitance — but watch breakdown.
• For PCB trace impedance, the effective dielectric constant depends on how much field is in the substrate vs air.
• Guard against dielectric absorption in precision circuits — some materials "remember" previous charge.

Dielectric Material Categories

**Gases**: Air (κ=1.0006), SF₆ (κ=1.002). Low κ but excellent self-healing after breakdown. SF₆ has 2.5× the dielectric strength of air. Used in high-voltage switchgear and gas-insulated substations.

**Polymers**: PE (κ=2.3), PTFE (κ=2.1), PVC (κ=3.4), polycarbonate (κ=3.0). Excellent dielectric strength (20-40 kV/mm), low loss, cheap. Most capacitor and cable insulation uses polymers. PTFE is the gold standard for RF applications.

**Ceramics**: Class I (C0G/NP0, κ=6-100): stable, low loss, low κ. Class II (X7R, κ=2000-4000): high κ but voltage/temperature dependent. Class III (Y5V, κ=4000-16000): highest κ but worst stability. Used in SMD capacitors — the most common capacitor type manufactured.

Capacitor Energy Density

Energy density = ½κε₀E², where E is the electric field limited by dielectric strength. To maximize energy storage: choose materials with both high κ and high dielectric strength. Barium titanate has very high κ but moderate breakdown strength. PVDF film has moderate κ but excellent breakdown strength and achieves excellent energy density.

Frequency Dependence

At low frequencies (DC to kHz), all polarization mechanisms contribute to κ: electronic, ionic, orientational (dipolar), and space charge. As frequency increases, slower mechanisms can't follow, and κ decreases. For water: κ drops from 80 (DC) to 5.5 (optical). For FR-4: κ drops from 4.5 (1 MHz) to 4.2 (1 GHz). Always use the dielectric constant at the operating frequency.

Frequently Asked Questions

• What is the dielectric constant?

  The dielectric constant κ (also called relative permittivity εᵣ) is the factor by which a material increases the capacitance compared to vacuum (κ=1). Air: κ≈1.0006, paper: κ≈3.5, glass: κ≈5-10, water: κ≈80, barium titanate: κ≈1200-10000. Higher κ means more charge storage per unit volume.

• Why does water have such a high dielectric constant?

  Water molecules are strongly polar — the H₂O molecule has a permanent electric dipole moment. In an electric field, water molecules align and create a strong opposing field that reduces the net field. This molecular polarization gives κ≈80. However, water is a poor practical dielectric because it's conductive (even deionized water absorbs CO₂).

• What is dielectric strength?

  Dielectric strength is the maximum electric field a material can withstand before electrical breakdown (arcing/shorting through the material). Measured in kV/mm or V/mil. Air: 3 kV/mm, PE: 20 kV/mm, mica: 40 kV/mm. Exceeding dielectric strength permanently damages most materials.

• How does temperature affect dielectric constant?

  Temperature effects vary by material. Ceramic dielectrics (especially Class II like X7R) change significantly — 15-25% over their rated range. C0G/NP0 ceramics are stable (<±30 ppm/°C). PTFE and polyethylene are very stable. Water's κ drops from 87 at 0°C to 55 at 100°C.

• What dielectric is used in PCBs?

  FR-4 (fiberglass-reinforced epoxy) is the most common PCB dielectric, with κ≈4.2-4.5 depending on resin content and frequency. High-speed designs use low-κ materials like Rogers (κ≈2.2-3.5) or PTFE (κ≈2.1). Lower κ reduces signal propagation delay and cross-talk.

• What is loss tangent (tan δ)?

  Loss tangent (dissipation factor) measures dielectric energy loss. Low tan δ means less energy wasted as heat. PTFE: 0.0002, PE: 0.0004, FR-4: 0.02, water: 0.04. For high-frequency RF circuits, low loss tangent is critical. FR-4 is poor above 1 GHz; Rogers or PTFE substrates are used instead.