A phone SAR value is the rate at which the body absorbs radio-frequency energy from a phone, measured in watts per kilogram of tissue. It is a compliance figure set by regulators, not a quality score for the handset.
The figure appears in manuals and on regulator databases, and it is one of the many numbers a buyer meets in the how to choose a smartphone guide.
SAR measurement basics
SAR stands for specific absorption rate. The FCC defines it as a measure of the rate that RF energy is absorbed by the body. The 1999 Council of the European Union recommendation on exposure limits describes the same quantity as the rate at which energy is absorbed per unit mass of body tissue, expressed in watts per kilogram.
The unit matters because it ties a phone’s radio output to a physical effect, heating, which is the effect the limits are designed to control. A phone does not simply have one SAR. The figure depends on where the phone sits relative to the body, which frequency band it is using and how much power it transmits, so manufacturers report the result of a defined test rather than a general property.
SAR applies to devices used close to the body. The FCC says that for devices intended for use near or against the body, such as phones and tablets, operating at or below 6 GHz, the guidelines specify exposure limits in terms of SAR. Above 6 GHz the FCC guidelines use power density as the relevant limit instead.
Lab testing procedure
Laboratories follow a standard procedure. According to the FCC, each phone is tested while operating at its highest power level in all the frequency bands in which it operates, and in various positions against a dummy head and body that simulate how people typically hold a phone.
The result is therefore a worst case. NTT Docomo’s compliance page for one of its phones makes the same point: the test is run at the phone’s highest certified power, but the actual SAR level of the phone while operating can be well below the maximum value, because the phone is designed to use only the power it needs to reach the network.
The FCC also notes that phones constantly vary their power and that operation at maximum power occurs infrequently. A test at maximum power gives a ceiling, not a typical daily figure, which is the main reason a SAR number should be read as a pass or fail against a limit.
US and European limits
Two limits cover most buyers. The US limit is set by the FCC and applies to phones sold there, while the European limit comes from a Council recommendation that manufacturers apply on the European market. The two use different averaging masses, so their numbers cannot be compared directly.
| Region | SAR limit for phones | Averaged over |
|---|---|---|
| United States (FCC) | 1.6 W/kg | one gram of tissue |
| European Union (Council recommendation) | 2.0 W/kg | ten grams of tissue |
The US figure comes from the FCC’s consumer guide, and the European figure comes from the compliance page of a phone maker that cites the Council of the European Union.
The FCC has required since 1996 that all wireless communications devices sold in the United States meet its guidelines, and says every device goes through a formal approval process to confirm it does not exceed the limits at its highest possible power level. The European limit, in the maker’s words, incorporates a substantial margin of safety to give additional protection for the public.
The FCC adds that all cell phones must meet a standard set at a level well below that at which laboratory testing indicates, and medical and biological experts generally agree, adverse health effects could occur. A phone that meets the limit is therefore compliant, whatever its exact number.
Limits of a single SAR figure
It is tempting to treat the lower number as the safer phone. The FCC advises against it. The SAR value reported in the manual and on the authorization indicates only the highest single measurement taken for each frequency range that the model uses, and the FCC states that phones cannot be reliably compared for their overall exposure characteristics on the basis of a single SAR value.
The FCC gives reasons. One phone might have a single high reading in a position that its user rarely uses, while another phone may be more efficient and operate at lower power in everyday conditions. Two phones that differ slightly on paper can therefore expose a person in the opposite order in practice.
Practical differences in exposure come from behaviour more than from the printed figure. The same FCC guide says the most effective means to reduce exposure are to hold the phone away from the head or body and to use a speakerphone or hands-free accessory, and that these measures generally have more impact than the small difference in SAR between individual phones.
Finding a phone’s SAR value
The FCC says the SAR values recorded on a phone’s authorization are also given in the phone’s manual. In the United States the FCC’s database holds more detail. The FCC says an FCC ID number is usually shown somewhere on the case of the phone or device, and that SAR information for many phones can be obtained from its database with that number.
Spec sheets for a handset list many figures, such as the sensor details covered in phone camera sensor size, and SAR belongs in the safety paragraph rather than the headline specifications. A handset’s compliance paperwork is also worth keeping with the box if a phone is later resold, a step in the how to sell old phone guide.
Health agency positions
The FDA shares regulatory responsibility for phones with the FCC. It states that the weight of scientific evidence has not linked cell phone radio frequency radiation with any health problems. The FCC says that, according to the FDA and the World Health Organization among others, to date there is no consistent or credible scientific evidence of health problems caused by exposure to radio frequency energy emitted by cell phones.
Readers who still want to reduce exposure can follow the FDA’s steps. In an archived copy of its page dated 14 December 2025 (the live page now redirects to the FDA’s general cell phones page), the FDA advised using speaker mode, headphones or earbuds to place more distance between your head and the phone and noted that the closer the device is to you, the more energy you will absorb. It also advised avoiding calls when the signal is weak, because this makes phones boost transmission power.
These points restate regulators’ guidance and are not medical advice. Anyone with an implanted medical device or a specific health concern should ask their doctor or the device manufacturer.
Frequently asked questions
Does a lower SAR mean a safer phone?
Show answer
Not necessarily. The FCC says SAR is the highest single reading from a test, so it cannot reliably compare overall exposure between phones. Every phone sold must meet the limit.
Why are the US and European limits different?
Show answer
They use different averaging masses. The FCC averages over one gram of tissue and the European recommendation uses ten grams, so the numbers are not directly comparable.
Is SAR measured during a real call?
Show answer
No. Laboratories test phones at their highest power against a dummy head and body in set positions, so the figure is a worst case for compliance rather than a record of everyday use.
How can exposure be reduced?
Show answer
The FCC says the most effective means are to hold the phone away from the head or body and to use a speakerphone or hands-free accessory. An archived FDA page from December 2025 also advised avoiding calls when the signal is weak, because phones then boost transmission power.
