Two popular gram scale apps – "Diamond Scale" for iPhone and "Digital Scale" for Android – require users to place a phone on an inflated plastic bag, calibrate, place a nickel at the top or bottom of the touchscreen, re-calibrate, and place the object to be weighed on the coin.
If your smartphone has an accelerometer or gyroscope, install “Diamond Scale” (iPhones, Leviteo, $1) or “Digital Scale” (Android phones, Aexol, $2.99). Free alternatives include “Weed Scale,” also by Aexol.
Launch the app, and place your phone on an inflated bag. One reviewer suggests using a bag of potato chips. Make sure that bag holds the phone steady, and then start the app’s calibrate function.
Once the app is calibrated, place a nickel (weighs five grams) on the screen of the phone outside the touchscreen, usually at the top or bottom of the phone’s screen. For instance, if your phone has a Home button, place the nickel there.
Let the app recalibrate, and check for accuracy. Reposition the phone, and recalibrate as necessary to help the app be as accurate as possible. Once you’re satisfied, very gently place the object you want to weigh on the nickel, and wait for the readout.