Jim Taylor, a research scientist with Google Health, knows a thing or two about taking temperatures. That’s because in addition to his role at Google, he’s also a pediatrician. “The first thing I ask a parent when they call and say ‘My child has a fever’ is ‘What’s their temperature?’” he says.

For six years, Jim has been part of the team at Google Health working to bring health tools to Pixel phones. One of the first of those tools is the new body temperature feature in the Thermometer app for Pixel 8 Pro. Part of the January Pixel feature drop, it allows you to quickly scan a person’s forehead with your phone and measure the body temperature. In clinical trials, our software algorithm was able to calculate body temperature in the range of 96.9°F – 104°F (36.1°C – 40°C) to within ±0.3°C when compared with an FDA-cleared temporal artery thermometer. In layman’s terms, this means the Pixel body temperature feature is about as accurate as other temporal artery thermometers.

Ravi Narasimhan, a research and development technical lead at Google, developed a miniaturized device that included an infrared sensor for body temperature measurement, which eventually evolved to become a feature for the Pixel phone. “You always have your phone with you, so it’s more convenient to measure body temperature without an additional device,” says Ravi.

Last month, we received the FDA’s De Novo classification for our body temperature app, the first for smartphones in the U.S. And as of this week, it’s now available on Pixel 8 Pro. Here’s a look at how the team built and tested it.

How we built the first smartphone body temperature app

Bodies emit infrared radiation — or, simply put, heat. The Pixel 8 Pro team added an infrared sensor to the phone next to the rear camera, which at launch was used to power the object temperature feature and now powers the body temperature feature as well. Measuring body temperature on the Pixel 8 Pro is simple: Just point the rear camera at the forehead and sweep across. The Pixel 8 Pro body temperature app accurately measures your temperature by scanning the temporal artery, unlike less accurate forehead thermometers that are pointed at the center of the forehead. The data from the infrared sensor is passed to an algorithm to calculate the temperature that will be displayed on your device, powered by the Tensor G3 chip.

The Pixel 8 Pro’s infrared sensor’s wide field of view (more than 130 degrees) causes it to sense heat beyond the forehead when the phone is too far away from the forehead. “It’s basically a big cone that the sensor takes in,” Ravi says. “Arteries are relatively small, so the closer you are, the more accurate reading you will get.”