It sounds like a simple question: How much is a college actually going to cost?

In fact, it’s a slippery one. But thanks to a federal mandate, a new tool to help students and families pin down an answer is finally arriving this month: a fairly simple online calculator to estimate what you can expect to pay to attend any college in the United States.

The new “net price calculators” — many already up and running on college websites ahead of the Oct. 29 legal deadline — are designed to provide the non-binding cost estimates based on a few relatively straightforward questions about family finances.

More broadly, they’re supposed to help students navigate one of the most confusing aspects of the college matchmaking process. While a school’s “list price” is usually easy enough to identify, students often don’t hear until long after they’ve applied and gotten acceptance letters what will be their “net price” — the sometimes substantially lower cost after scholarships and discounts are applied.

That could lead to more students considering high-priced private institutions where applicants are often scared off by sticker price shock.

Colleges may generally lean left politically, but when it comes to Washington mandates they quickly turn into anti-government zealots. So when Congress forced all institutions that receive federal dollars — including community colleges and for-profits — to start developing the calculators in 2008, most were opposed.

But since then, opposition has mellowed into grudging acceptance and even enthusiasm.

Not all educators are supportive. Kent Barnds, vice president of enrollment, communication and planning at Augustana College in Illinois, fears the calculators will lead to the further “commodification” of a college education, pitting price-shopping families against schools and de-emphasizing whether a school’s cost reflects its value. But even he acknowledges some upside.

“Once upon a time, [colleges] were much more comfortable saying, ‘just apply and we’ll tell you what it costs in April,’” he said. “That’s no way to do business.” The net price calculator is “going to force us to be more careful in how we talk about our costs, and talk about it earlier.”

Colleges themselves will probably be regular users, trying to discern what competitors are offering. But that competition will ultimately benefit students, said Daniel Lugo, head of financial aid at Franklin and Marshall College in Pennsylvania.