SAR (Specific Absorption Rate)

The Specific Absorption Rate (SAR) measures the rate at which radio frequency (RF) energy is absorbed by human tissue when exposed to electromagnetic fields from wireless devices. It is expressed in watts per kilogram (W/kg) and serves as a key safety metric for evaluating electromagnetic exposure.

Need to verify SAR compliance for your wireless device? Learn more about accredited testing procedures and exposure limits on our SAR testing services page.

Regulatory Limits and Compliance

SAR values are essential for demonstrating compliance with human exposure limits defined by regulatory bodies.

• European Union: 2.0 W/kg (averaged over 10 g of tissue)

• United States (FCC): 1.6 W/kg (averaged over 1 g of tissue)

These limits help ensure that wireless devices are safe for everyday use.

Calculation of SAR

SAR is calculated using the formula:

SAR = σE² / ρ

where:

• σ = tissue conductivity (S/m)

• E = electric field strength (V/m)

• ρ = tissue density (kg/m³)

Practical Example

Most modern smartphones have SAR values between 0.5 and 1.5 W/kg, measured at the head or body using standardized test conditions. Before market approval, manufacturers must verify and report these values as part of the regulatory process.

Application in Product Certification

SAR testing is mandatory for the certification of:

• Mobile phones

• Tablets

• Wearables and IoT devices

• Wireless communication equipment

It ensures that devices meet exposure safety limits in accordance with national and international standards.