Enter your Electric Field (E), Conductivity of Material (σ), and Mass Density (ρ) into this SAR Calculator to find the Specific Absorption Rate — how much electromagnetic energy a material absorbs per unit mass. You'll also get Incident Power Density and E² as supporting outputs.
Specific Absorption Rate (SAR)
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Incident Power Density
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Electric Field² (E²)
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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.
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).
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.
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.
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.
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.
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.
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.