Free Age Difference Calculator
Your exact age gap in years, months and days — and how common it is, from U.S. Census couples data. Free, no sign-up.
You and them
Everything is worked out in your browser. Birthdays are never uploaded, stored, or put into a shared link.
Fill in both sides to see the age difference.
How this is calculated
Two birthdays are counted the way a calendar counts them: whole years first, then whole months, then the days left over, using real month lengths and leap days. Enter an age instead of a birthday and only the year difference is knowable, so the result says "about".
- How common each gap is
- U.S. Census Bureau, Current Population Survey, 2023 Annual Social and Economic Supplement — America's Families and Living Arrangements: 2023, Table FG3. It covers 63.9 million opposite-sex married couple family groups; same-sex married couples are not in this table, and its narrowest bin is "within 1 year". Census table
- "Half your age plus seven"
- Frederick Locker, Patchwork (1879), page 88 — the earliest printed version we could verify, written as advice on the right age for a wife, and already carrying the joke about the upper end. Max O'Rell repeated it in 1901 and presented it as something he had heard, not his own. 1879 original
- What happens over time
- Wang-Sheng Lee and Terra McKinnish, "The Marital Satisfaction of Differently Aged Couples", Journal of Population Economics 31(2), 2018 — 3,374 Australian couples followed from 2001 to 2013. Paper
Honest fine print: the Census bins are wide, so "6 or more years apart" is the finest read available for a 7-year gap. That data describes married couples living together, which is not the same population as people who are dating. And none of it says anything about one specific relationship.
Age gaps, answered
What is the "half your age plus seven" rule, and does it mean anything?
It is a Victorian rule of thumb. The earliest printed version we could find is Frederick Locker's Patchwork in 1879, offered as advice on the right age for a wife; the 1901 book usually credited with it explicitly says the author heard it from someone else. No study has ever tested the formula. A Psychology Today analysis that laid it over survey data on stated partner preferences found it roughly matched what men said their minimum was, and missed what women said theirs was.
How much of an age gap is too much?
There is no number that answers this, and a calculator cannot supply one. What tends to matter is life stage rather than years: two people ten years apart at 45 and 55 are usually in the same chapter of life, while 19 and 29 rarely are. This page gives you the number and how common it is. The rest is not arithmetic.
Is a 10-year age gap common?
About 8% of U.S. married couples are ten or more years apart, and a little over 1% are twenty or more — so a decade is uncommon without being rare, roughly one married couple in twelve. Gaps are also wider in remarriages than in first marriages: Pew's analysis of 2022 American Community Survey data found 56% of remarried husbands have a wife three or more years younger, against 35% of husbands in a first marriage.
Are age-gap couples more likely to break up?
Wider gaps do correlate with higher divorce rates in large surveys, but the exact percentages that circulate online — a ten-year gap means 39% more divorce, and so on — come from a blog re-analysis whose author later added a note saying the underlying study cannot support them. A 2018 study of 3,374 Australian couples found something subtler: partners married to someone younger started out more satisfied, and that advantage disappeared within six to ten years of marriage, for husbands and wives alike.
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