You may pay nearly $8 for a McDonald's Big Mac in Massachusetts versus $3 in Okl...

• High inflation and commodity costs are forcing chains to raise menu prices.

• A New York college student created a searchable fast-food index to highlight prices in the US.

• The index shows how prices vary for chains like Chipotle, McDonald's, Chick-fil-A, and Taco Bell.

Riley Walz is a business major at the Macaulay Honors College at the City University of New York and dabbles in coding. The 20-year-old one day hopes to run his own business. Until that happens, he's taken on the unofficial position of "fast-food data scientist," thanks to his latest side project, the Fast Food Index.

Walz's index, distributed to classmates last month, tracks the pricing of four popular fast-food items: McDonald's Big Mac, Taco Bell's crunchy taco, Chipotle's chicken burrito, and Chick-fil-A's chicken sandwich. He created the searchable index last month after noticing his go-to chicken burrito from a Chipotle near Columbia University cost 15 cents more than his neighborhood Chipotle on the Upper East Side.

As a business student, he understands that cost of living plays a factor in menu pricing, but he wondered why prices of the same item would vary that much from one part of the city to another.

"I was interested to see where's the cheapest burrito in the entire country and where is the most expensive one," he told Insider.

Three weeks later, he had his answer.

According to the Fast Food Index, the most expensive Chipotle chicken burrito is sold for $11.10 in Manhattan's garment district. There's a three-way tie for the cheapest burrito in Iowa City, Iowa; Athens, Ohio; and Ann Arbor, Michigan.

To create the index, he wrote a script that scraped menu data from the apps of each chain.

"It just kept making a request, pretending it was going to make an order at every single store," he said of the script.

The index is searchable by Zip Code and highlights the average price of all four menu items in the US and the three cities where each item is the most and least expensive.