What’s the hardest part about leaving tips when you travel? Figuring out how much to give, of course. Now some tipping apps can take the guesswork out of it for you.

Tipulator, for iOS and Android devices, is a simple tool that lets you choose your amount—from zero to 25 percent—and calculates how much that is.

It tallies up the entire bill, including the tip, and then you can split that amount with your dining partners. No calculators needed.

Gratuities is a similar app that works for restaurants, food delivery businesses, and even taxis.

Of course, with more and more people paying for goods and services digitally, it can be easy to overlook the tip.

At Starbucks, they solved the tipping issue with a payment app. You have a two-hour window to tip your barista through your smartphone or tablet.

But while we can expect to see this kind of tool become more commonplace, I have some advice: When you’re traveling, cash is still king.

Trust me, your bellman, your hotel maid, and in some places, even your taxi driver, won’t have digital card readers on hand.

For more information, visit the Apps & Technology Archives.

Keep reading for more travel tips.