Specific Absorption Rate (SAR)

What is SAR and What are SAR Limits on Electromagnetic Radiation?

Updated July 15, 2026

 

About SAR (Specific Absorption Rate)

 

SAR, or Specific Absorption Rate, is a measure of the amount of Radio Frequency (RF) Electromagnetic Fields (EMFs) absorbed by the human body when using an electronic device.

 

This rate is measured as the power absorbed within a defined area of body tissue in a standard measurement of watts per kilogram (W/kg).

 

SAR can be an average measure over the entire body, or a small sample amount. What you get is the greatest level measured in a defined area of the body.

 

"The value is highly dependent upon the body parts being tested, energy levels and the proximity to the radiating source.

 

The SAR value is established by selecting areas of the body to be tested, finding the highest absorption rate while exposing that area closest to the radiating source.

 

There are guidelines for SAR established by national and international organizations.

 

"Current" SAR standards (from 1966!) measure exposure within the frequency range of 100 kHz and 10 GHz which includes electronic devices such as laptops, tablets, WiFi routers and cell phones.

 

For example, below are SAR requirements for cell phones, set in 1993, which became adopted by the Federal Communications Commission (FCC) in 1996. Back then, only a small fraction of the population were using cell phones, and only for minutes of the day.

 

SAR Guidelines

 

United States SAR Limits

 

In the US, the Federal Communication Commission (FCC) requires that cell phones have a SAR level at or below 1.6 watts per kilogram (W/kg) taken over a volume containing a mass of 1 gram (g) of tissue.

 

This limit was established to prevent tissue heating (thermal effects) and has not been meaningfully updated since 1996. Critically, these standards fail to account for non-thermal biological effects. A 2025 Yale study found severe disruptions to human brain cell development at RF exposure levels 4,000 times below the FCC’s 1.6W/kg limit, at just 0.025% of what regulators consider “safe”. The research demonstrates that biological harm occurs at levels far below what SAR limits were designed to protect.

 

European Union SAR Limits

 

The EU has set SAR limits for mobile phones (and other such hand-held devices), to be less than or equal to 2 W/kg averaged over 10 g of tissue.

 

Like the FCC standard, the EU limit is based solely on preventing short-term tissue heating and does not address non-thermal biological effects now documented in peer-reviewed research. The Yale findings apply equally here: harm to developing brain tissue occurs at exposure levels thousands of times below this regulatory threshold. 

 

Since regulatory SAR limits have not kept pace with the science, the most practical path to reducing your exposure is to lower it directly at the source. DefenderShield's EMF-blocking phone cases and laptop shields are built with Ultra Armor+® shielding technology, independently lab tested to block up to 99% of RF and ELF radiation, including the full 5G spectrum, at the point of contact with your body. You can review the complete independent lab testing results to see exactly how our shielding performs against the frequencies discussed above. If you want a deeper look at the science behind our shielding materials, our technology page breaks down how each product line is engineered to protect you where outdated regulations fall short.

 

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