An iPhone emits radiofrequency electromagnetic fields (EMF) at levels measured in watts per kilogram of body tissue, a unit called SAR (Specific Absorption Rate). For a current model like the iPhone 15 Pro, the SAR at your head measures between 1.10 and 1.14 W/kg, and body exposure sits around 1.16 to 1.17 W/kg. These figures fall below the FCC’s legal limit of 1.6 W/kg, though they represent close to 70% of that ceiling. The actual EMF your phone puts out at any given moment varies dramatically depending on what you’re doing with it and how strong your cellular signal is.
SAR Values for Recent iPhones
Every iPhone sold in the U.S. must be tested and certified to stay below the FCC’s SAR limit of 1.6 W/kg, averaged over 1 gram of tissue. Countries following the European standard use a slightly different measurement (averaged over 10 grams of tissue) with a limit of 2.0 W/kg. Apple publishes SAR data for every model on its regulatory information pages.
For the iPhone 15 Pro, the numbers break down like this:
- Head SAR (U.S. standard): 1.10 to 1.14 W/kg, depending on the specific model variant
- Body SAR (U.S. standard): 1.16 to 1.17 W/kg
- Head SAR (European standard): 0.98 W/kg
- Body SAR (European standard): 0.96 to 0.98 W/kg
These are worst-case maximums recorded during testing, not what the phone typically emits during a regular call or while browsing. In real-world use, the phone’s output is almost always lower. Still, these maximums give you a useful comparison point between models and against the legal ceiling.
How Testing Works (and Its Limits)
FCC testing measures SAR at a fixed distance from the body. For iPhones going back to the iPhone 7, body-worn SAR testing has been conducted at 5 millimeters from the skin. That’s roughly the thickness of a thin phone case. Head SAR testing simulates a phone pressed against the ear. If your phone sits directly on your skin with no case, or if you carry it in a tight pocket with less than 5mm of separation, your actual exposure could exceed the tested values.
This testing gap made headlines in 2023, when France’s telecom regulator (ANFR) found the iPhone 12 exceeded SAR limits under their off-body testing protocol. The issue involved a feature where the iPhone slightly increases its transmission power when it detects it’s not against a body, such as sitting on a table. Apple released iOS 17.1 with a software update specifically for iPhone 12 users in France that turned off this power increase, resolving the regulatory concern without recalling any hardware.
What Makes Your iPhone Emit More or Less
The SAR numbers Apple publishes represent the phone transmitting at maximum power. In daily use, your iPhone constantly adjusts its output based on conditions. The single biggest factor is signal strength. When your phone has a strong connection to a nearby cell tower, it needs very little power to communicate. When signal is weak, the phone compensates by boosting its transmission power significantly.
Research measuring this relationship has found a clear negative correlation: as signal strength goes up, RF exposure goes down. During data uploads, for instance, each improvement in signal strength produces a measurable, proportional drop in the EMF your phone sends toward your head or chest. The practical takeaway is straightforward. Using your phone in a basement, elevator, rural area, or moving vehicle where signal bars are low means your phone is working harder and emitting more RF energy than the same phone used next to a window in a city.
The type of activity also matters. A phone in standby or receiving data emits very little. Voice calls, video uploads, and anything that requires the phone to transmit data back to the tower will increase output. Speakerphone and wired headphones create distance between the antenna and your body, which reduces exposure by the inverse square law: doubling the distance cuts exposure to roughly one quarter.
5G vs. 4G Emissions
If your iPhone is connecting over 5G instead of 4G, it likely emits more RF energy during active use. Measurements comparing the two technologies found that electric field strength at 10 cm from a phone was about 60% higher on average during 5G transmissions compared to 4G. For certain activities, the gap was even wider: during video streaming, 5G field strength was roughly three times higher than 4G.
The signal patterns also differ. 5G transmissions tend to have sharper, more intense power peaks. During file downloads, these peak-to-average ratios were nearly double what 4G produces. One notable difference is that 4G emission patterns vary a lot depending on what app or activity you’re running, while 5G emissions are more uniform across different tasks. This is partly because 5G uses more advanced modulation and antenna techniques that produce a more consistent but generally higher-powered signal.
These measurements reflect the sub-6 GHz band of 5G (called FR1), which is what most people actually connect to in everyday use. Millimeter-wave 5G, the faster variant available in limited areas, operates at higher frequencies that penetrate skin less deeply but is far less commonly encountered.
Practical Ways to Reduce Exposure
Since EMF intensity drops sharply with distance, the simplest way to lower your exposure is to keep the phone away from your body when it’s actively transmitting. Using speakerphone or wired earbuds during calls makes a substantial difference compared to holding the phone against your ear. Carrying the phone in a bag rather than a pocket adds distance during the times it communicates with cell towers in the background.
Choosing environments with strong cell signals helps too. If you notice one bar of signal, your phone is compensating with higher power output. Switching to Wi-Fi calling when available generally lowers transmission power because your router is much closer than the nearest cell tower. Texting instead of calling also reduces exposure, since the phone transmits in short bursts rather than maintaining a continuous connection at your head.
Airplane mode eliminates RF emissions entirely, which is useful at night if you keep the phone on your nightstand. With airplane mode on, the phone’s cellular, Wi-Fi, and Bluetooth radios all shut down, dropping EMF output to essentially zero from the wireless transmitters.