SAR Calculator (Specific Absorption Rate)

The SAR Calculator measures how much radiofrequency (RF) energy is absorbed by biological tissue per unit of mass — a key safety metric used in evaluating exposure from devices like mobile phones and medical equipment. Enter the Electric Field (E), Conductivity of Material (σ), and Mass Density (ρ) to calculate the Specific Absorption Rate in W/kg. Secondary outputs include Incident Power Density and Electric Field² (E²).

V/m

RMS value of the electric field strength

S/m

Electrical conductivity of biological tissue

kg/m³

Mass density of the biological material

Results

Specific Absorption Rate (SAR)

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Incident Power Density

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Electric Field² (E²)

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Frequently Asked Questions

What is Specific Absorption Rate (SAR)?

SAR is a measure of the rate at which RF energy is absorbed by human tissue when exposed to electromagnetic fields. It's expressed in watts per kilogram (W/kg) and is crucial for assessing RF exposure safety.

How is SAR calculated?

SAR is calculated using the formula: SAR = (σ × E²) / ρ, where σ is the conductivity of the material (S/m), E is the electric field strength (V/m), and ρ is the mass density (kg/m³).

What are typical SAR limits for mobile devices?

In the US, the FCC limit is 1.6 W/kg averaged over 1 gram of tissue. In Europe, the limit is 2.0 W/kg averaged over 10 grams of tissue. These limits ensure safe exposure levels.

What factors affect SAR values?

SAR values depend on the electric field strength, the electrical conductivity of the tissue, and the mass density of the material. Higher conductivity and electric field strength increase SAR, while higher density decreases it.

What is the relationship between SAR and power density?

Power density represents the electromagnetic power per unit area and is calculated as E²/377. It's related to SAR but measures the incident power rather than the absorbed power in tissue.

Why is SAR measurement important for RF safety?

SAR measurement is essential for ensuring that RF devices comply with safety standards and don't exceed exposure limits that could cause thermal heating effects in human tissue.

What are typical conductivity values for human tissue?

Human tissue conductivity varies: muscle tissue is around 0.3-0.8 S/m, brain tissue is about 0.15-0.45 S/m, and bone tissue is much lower at 0.02-0.1 S/m.

How does frequency affect SAR calculations?

While this calculator uses general SAR formulas, actual SAR values are frequency-dependent due to tissue properties changing with frequency. Different frequencies penetrate tissue to different depths.