Iced coffee can hit the spot on a warm summer day, but are you really getting your money’s worth?

There’s a secret ordering trick that a lot of people use at Dunkin’ Donuts and other popular coffee chains to get the most bang for their buck.

What exactly is that secret? Just ask for “light ice.”

Read more: 5 big changes coming to Dunkin’ Donuts in 2017

Ask for light ice when ordering an iced coffee

When I heard about this hack for the first time, I was skeptical. How much of a difference can the ice really make? So I went to my local Dunkin’ Donuts drive-thru and placed this order:

• One small iced coffee with skim milk
• One small iced coffee with skim milk and light ice

I’ll admit that I was afraid the person taking my order would judge me, but she understood my order — and even called me “sweetie!”

Once I got back to the office with my iced coffees a few minutes later, I used a measuring cup to see how much coffee was in the cups after removing the ice.

Here’s what happened:

The coffee with light ice (left) was not filled up to the very top like the one with regular ice.

My co-worker Beth helped pour the coffee into a measuring cup. 

The iced coffee with light ice had 13.5 ounces of coffee. 

The iced coffee with regular ice had just 11 ounces of coffee, a 2.5 ounce difference.

We put the coffee back into the Dunkin’ Donuts cups without the ice for this side-by-side comparison.

Read more: 7 cheap brands of coffee that people really love

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