Touchscale is website that allow you to weigh things on your iPhone. It use your 3D Touch Device as a scale. The iPhone weighing function can only be used on models that support 3D Touch. From iPhone 6s/6s Plus until the latest model. As for the iOS version, there is no limit.
How to setup iPhone for weigh scale
First go to iOS Settings > Accessibility > Touch. Select 3D and touch feedback touch, and turn on 3D touch. Open the TouchScale webpage directly through the iPhone browser, and you can place items on the iPhone to measure the weight.
Things to consider
Please pay extra attention not to put metal or heavy items to avoid cracking or leaving the screen scratches. Also, whatever you’re weighing need to be conductive to activate the touchscreen sensor. For example you can’t weigh a plastic bottle because the phone doesn’t recognize there is anything touching the screen. So you need something like a spoon on the screen to trigger the iPhone and place the plastic bottle on top of the spoon. To weigh the plastic bottle, simply deduct the spoon weight.
Last but not least, compare it with an electronic scale, you will find that it’s not so accurate, so just play and entertain.