Math is hard. Like really, really hard. Especially when it comes to tipping. But don't break out the already-loaded calculator app out on your phone. Don't even think about looking at the total, moving the decimal point over one place, and then multiplying that number by two. No. There's an app for that, thanks to Gratuity.
See Also: Is it Ever Okay Not to Tip?
The free tip calculator app is, according to the company, popular due to its interface and animation. While it can also help split checks and tabs between large parties, the main draw is taking the math out of tipping.
All you have to do is decide if you feel smiley face about your service or frowny face about your service and then also pick what kind of establishment you're at and also enter in the total. Actually all of that comes after you've already changed the settings in the app to reflect your tipping preferences.
But seriously, it's just that easy. Almost as easy as basic math. Gratuity is available in the App store for Apple products.