Choosing a college is one of the most important financial decisions that a teenager — and his or her parents — will ever make. But families that are going through the college-application process have usually had little in the way of meaningful cost estimates to guide them.

The official “sticker price” of an institution is what dominates most kitchen table discussions, but most students don’t pay anywhere close to that amount. Grants, scholarships and other forms of financial aid can radically alter the all-important “Which school is most affordable?” question. Some private colleges, especially those with large endowments, offer generous aid packages that can make going to Harvard cheaper than attending a state university.

Now, in response to new federal requirements, every accredited college and university across the country — about 7,000 in total — must post on their websites a “net price calculator” that estimates how much out-of-pocket expenses a prospective student will incur. The calculator projections are based on a student’s academic qualifications and family income, and allow families to stop talking about sticker price and start talking about the number that really matters: their price.

“The net price calculators provide a new level of transparency that wasn’t there before,” said Diane Cheng of the nonprofit Institute for College Access & Success, a student advocacy group. “You can’t know from a sticker price how much you as an individual student and your family will pay.”

Just estimates

College financial aid administrators are quick to point out that the calculator projections are just estimates. College financial aid award letters, which are sent out in the spring, could offer more or less financial aid than a school’s calculator predicts.

But the online calculators win points for timing. Students use the fall and winter months to send out college applications, so by the time award letters arrive, it is too late to add other schools to the mix. By checking the net price calculators now, students and families benefit from additional financial information while there is still a window of opportunity to apply elsewhere.

It is important to remember, however, that differences of several hundred — or even thousand — dollars between school calculators aren’t the final word on price. Some calculators do not include all aid programs.

Florida’s state universities, in projecting aid totals, sometimes include the state’s Bright Futures program, and sometimes they don’t. This means that families should mentally fill in the gaps as they use the calculators, and factor in student aid they know they are going to get, even if the calculator missed it.

The calculators vary widely in quality and format — some asking only a few multiple-choice questions, others asking for detailed financial information that will require you to have your tax return in hand.

The differences between calculators means that apples-to-apples comparisons are difficult, if not impossible, to obtain.

Take Nova Southeastern University in Davie. The school’s $22,650 annual undergraduate tuition could potentially discourage some students from applying, but Nova’s net price calculator reveals financial aid programs that are not common knowledge.

Among them: Nova offers recipients of Florida’s top-level Bright Futures scholarship (the Academic Scholars Award) a guarantee that their full tuition will be covered without any student loans. For those students — who have seen the Legislature reduce the value of their scholarship when it is used at public institutions — an NSU education could prove to be far cheaper than anticipated.

Elaine Brenner, NSU’s associate director of enrollment and student services, said the calculators can be particularly helpful to first-generation college students and their families — a group that can sometimes be intimidated by the complicated financial aid process.

“There’s so much criteria, little tiny things, and they change every year,” Brenner said. “It’s just like this whole other world.”

Brenner estimated that NSU’s calculator, which is more detailed than some, will take a family about 10 to 15 minutes to complete.

At UM, a shorter list

At the University of Miami, administrators focused on simplicity.

James Bauer, UM’s executive director of financial assistance services, said UM opted for a shorter list of calculator questions because there’s too much uncertainty when it comes to various government-funded aid programs. Congress is considering reductions in Pell Grants for needy students, while state lawmakers in Tallahassee have been scaling back Bright Futures scholarships year after year.

“What you get in terms of an actual award may look very different,” Bauer said. He urged families not to overreact if a school’s calculator spits out numbers they don’t like. Bauer sees the calculator’s purpose as nudging families to always apply for financial aid, and to take a second look at private universities that may have a high sticker price.

“If it discourages you, don’t put too much stock in it,” he said.