The Arithmetic of Adulthood

As a kid, you teasingly sang about three very grown-up milestones: love, marriage, and the baby carriage. We crunched the numbers to see just how these upheavals tip the scales in the rest of your life.

A New Relationship

-2 confidants

Singles' social circles contain one more friend and one more family member than those of folks in serious relationships, according to a study from the University of Oxford. Devoting energy to a new bf or gf limits the time we can devote to maintaining other relationships, and could push close contacts to the periphery.

-2 letter grades in school

Teen girls' GPAs drop when they enter relationships, while girls who stay single throughout the semester see their grades improve, according to research from the University of Texas at Austin. Romantic entanglements dock school engagement for boys, too, but not enough to affect their marks. Boys may just consider high school sweethearts less important.

Getting Married

-3-6 drinking binges per year

Does that bachelor party really mark the end of juvenile buffoonery? Marriage puts a damper on certain "bad behaviors," research from Northwestern University shows. People "clean up their act" after tying the knot, perhaps due to social expectations about how married adults are supposed to behave.

+4 pounds

Newlyweds gain more weight in the first two years of wedded bliss than those who stay single, notes a study in Nature. Marriage may reduce the drive to stay slender.

Becoming a Parent

-$222,360

A child born in 2009 will cost middle class parents nearly a quarter-million dollars to raise, excluding the price of college, according to a recent USDA report. Thankfully, the costs per kid decrease with each additional sibling.

+9 hours of housework per week

Childless young women average 22 hours of housework a week (including grocery shopping and paying bills), while women with young kids put in 31 hours, University of Maryland scientists say. Men's weekly contributions hold steady at 21 hours. Moms also report having more conflicts with their spouses, while dads don't note a change. Why the discrepancy? "Women are probably asking their husbands to help out more," says researcher Kei Nomaguchi. "Women see it as a disagreement, and men see it as their wife complaining."