Measuring slope angle, to assess avalanche potential or brag about how steep that final couloir was to your friends, can be useful in the backcountry.

The old-school way of doing this was with a sort of plumb bob on fancier compasses called a clinometer. Truth is, using one is often a hassle. You may find it hard to read the tiny numbers on the compass, and usually have to have your cheek down in the snow to be able to look at the compass. About the only advantage is that it doesn't need batteries.

A more modern and way easier way to check slope angle is with some sort of “Measure/Level” app on your phone. The iPhone has one built in to the operating system. Or, you can get a free measurement tool from BCA Backcountry Access. (Android folks, I'm sure you can find something similar.)

Open the Measure/Level app on your iPhone, and swipe to open the Level app. If you're walking / skinning uphill, simply put the phone flat on your ski, or on edge if going across the slope.

Note: Just knowing the slope angle is not the whole story as far as avalanche potential. Avalanches are often caused by micro terrain features that you may not notice by taking a quick measurement like this. Or, you could be on a safe slope, but there could be an unsafe slope above, with you in the run out zone.

At top is a photo showing how it's done, from the expert backcountry ski guides at Graybird Guiding. (Note, an uphill skin track of about 18° is thought to be about optimal, so keep that number in mind.)

Note that phones don't behave well in the cold. If you use it for occasional slope measurement, try to put it back in an inside pocket, ideally in your base layer between uses. Carrying an auxiliary battery at full charge, also kept warm, with a short charging cable, is highly recommended.

If you have an iPhone, this measuring tool is free as part of the operating system.

However, for just a few bucks more, you can get an iPhone and Android app that's quite a bit better. Search the App Store for “Avalanche Inclinometer” (made by Iterum LLC). As of winter 2024, this app is $3.99.

This upgrade has some handy and easy to read features: the slope value is color coded to remind you when you might be getting into higher risk terrain, you can tap to lock the screen, and it also shows your elevation, aspect, and coordinates. With a tap you can share all this information via email.