Nike is updating its app with a new augmented reality tool that will measure your feet so that it can sell you sneakers that actually fit (via Engadget).

While this may seem like a frivolous use of AR technology, the idea is sound. Buying shoes online is difficult, mainly because you can’t try them on to see if they actually fit. Plus, brands lie about sizes, so you can never really be sure. For example, you may be a size 12 in one brand but a size 11 in another brand.

Nike shoes, in particular, famously run small in most styles, making them extra hard to buy, even if you do happen to have a Brannock device handy to know your foot’s measurements down to the millimeter.

Taking the guesswork out of buying shoes online

With this new AR feature, Nike says it can measure each foot individually — the size, shape, and volume — with accuracy within 2 millimeters and then suggest the specific size of Nike shoe for the style that you’re looking at. It does this by matching your measurements to the internal volume already known for each of its shoes, and the purchase data of people with similar-sized feet.

It’s not just a one-time gimmick, either: Nike is integrating this into its app as a primary feature for measuring shoes, and it will be using it at its retail stores as well, which speaks to the company’s confidence in the method.

The update should be rolling out in Nike’s app in July in the US, and there are plans to bring the feature to Europe in August.