@user1657 has given an interesting answer to a question of @ArghyaChakraborty. He says that the Android app called "Analyze your games" can estimate the user's Elo strength.
How would it do that?
You're probably not going to offer me a master's thesis on the mathematics of Elo-rating estimation here, but I'd be interested in a vague outline of the mathematics, or of the technique, if you happen to know it.
Or maybe you'll close this question as off-topic. It's kind of on the borderline, I'll admit. But, still, a computer estimating your chess strength, so that you know whether you're ready to take Karjakin's seat against Carlsen? That's pretty cool.