# SAR Testing Explained: RF Exposure Limits for Wearables and Phones

SAR — Specific Absorption Rate — is the measure of how much radio frequency energy is absorbed by human tissue when a device is used close to the body. SAR testing is mandatory for any wireless device worn on or used against the body, and the EU and US limits are not the same. Missing SAR in your test plan means a failed certification and a delayed launch.


## Transcript

### If it touches the body, SAR testing applies

SAR testing is one of the most commonly missed items in wireless certification. Worn on the wrist, in a pocket, against the ear — anything within 20 centimetres of the body needs SAR testing, mandatory for CE in the EU and FCC in the US.

### SAR limits and when they apply

SAR measures RF energy absorbed by body tissue, in watts per kilogram. In the EU, under EN 50566, the limit is 2 watts per kilogram over 10 grams. In the US, FCC's limit is 1.6 watts per kilogram over 1 gram — stricter at higher frequencies. Testing triggers at 20 millimetres separation or less, covering phones, watches, and wearables.

### Planning SAR into your test campaign

Add SAR to your test plan alongside RED and FCC testing — same RF configurations, often run concurrently, saving time and cost. Declare your separation distances in the user manual first, since the SAR setup must match them. Test at the closest declared distance.

Tags: SAR testing, RF exposure, wearables, CE marking, FCC