Numbers and rankings are everywhere. We add up our Twitter followers and Facebook friends. We use standardized test scores to evaluate teachers and students.

“Numbers make intangibles tangible,” said Jonah Lehrer, a journalist and author of “How We Decide.” “They give the illusion of control.”

Many people shopping for cars, for example, get fixated on how much horsepower an engine has, though in most cases it doesn’t matter, Mr. Lehrer said.

“We want to quantify everything,” he went on, “to ground a decision in fact, instead of asking whether that variable matters.”

We often do need to find ways to measure and evaluate people and as objectively as possible. The trouble, though, is when we mindlessly rely on those numbers to tell us everything, said Sherry Turkle, director of the Massachusetts Institute of Technology’s Initiative on Technology and Self. Numbers become not just part of the way we judge and assess, but the only way.

“One of the fantasies of numerical ranking is that you know how you got there,” said Professor Turkle, who is the author of “Alone Together: Why We Expect More From Technology and Less From Each Other.” “But the problem is if the numbers are arrived at in an irrational way, or black-boxed, so we don’t understand how we got there, then what use are they?”

My colleague Michael Winerip recently wrote an article about an excellent middle-school teacher, with terrific performance evaluations. But a formula used by the New York Department of Education put the teacher in the seventh percentile of her teaching peers.

The formula used 32 variables plugged into in a statistical model that “appears transparent, but is clear as mud,” Mr. Winerip wrote.

And even if we understand the numbers, they aren’t always helpful. Robin Black, author of the short story collection “If I Loved You, I Would Tell You This,” wrote a blog post on how fretting about the different ways of measuring her book’s success has overshadowed why she wrote it in the first place.

“I go to a place where everything has a number,” she told me. “How many advance copies, how many reviews, how many sales.”

At Amazon authors can check how many books they’ve sold and, using interactive maps, even zero in on how many sales occurred in which cities.

Once, she said, “maybe every Sunday you looked at The New York Times best-seller list. Now you can torture yourself 24 hours a day, seven days a week.”

And the statistics really tell us almost nothing. Amazon’s rankings, for instance, can vary wildly based on the sale of very few books.

All those numbers help us lose sight of why we’re really doing what we’re doing. Ms. Black, for instance, said her books were largely about loss.

“I’ll get a letter from someone who says, ‘My daughter died, and reading your book really helped,’ ” Ms. Black said. “That’s so meaningful. How do I measure that against 500 Twitter followers?”

Eric Frankel is founder of a company called 10 Minutes to Change, which figures out how to improve workers’ performance.

He’s also a certified public accountant, so he knows the importance of numbers. But, he said: “Just because we have the skills and ability to put metrics on everything, doesn’t mean we should. People are ever-changing, fascinating and incredibly frustrating.”

This reliance on numbers is to some extent generational, said Howard Gardner, a professor of cognition at Harvard Graduate School of Education.

“For almost anybody in the United States under the age of 25, the only models are quantifiable rankings,” he said.

So when students are researching a paper, he said, they often look at which articles or papers online have the most hits.

“Should it be that whatever has the most hits or the most editors makes it better than someone who spent his life studying Kant?” he asked.

The obsession with numbers, he said, means we don’t trust or even look for the intangibles that can’t be measured, like wisdom, judgment and expertise.

We also lose a sense of ourselves as anything but a rank, and start feeling bad if our numbers don’t measure up to others.

In a blog post, Mr. Lehrer wrote: “What I’m most troubled by is the desire of individuals (especially myself) to constantly check up on these numbers, and to accept these measurements as a measure of something meaningful.” He went on, “That’s why I wish there was a popular social platform that didn’t measure anything.” It would, he wrote, “be a relief.”

(By the way, 320 people “liked” that blog post.)

Or as Ms. Black put it: “I have to stop worrying about numbers. I have to reclaim the ambiguous part of my own intelligence.”