The Half Your Age Plus 7 Rule, Explained
The rule is simple: the youngest person you should date is half your age, plus seven. A 30-year-old, by this arithmetic, should not date anyone under 22.
It is one of the most quoted formulas in dating — and one of the most misunderstood. This page works the formula at real ages, traces where it came from, and shows what the research actually says about it.
Worked Example: the Rule at Different Ages
At 20, the rule sets a floor of 17. At 30 it is 22. At 40 it is 27. At 60 it is 37. Notice what the formula is doing: the older you get, the faster your floor rises — the permitted gap grows from 3 years at 20 to 23 years at 60.
Run in reverse, the rule also sets a ceiling: the oldest person a 22-year-old should date, according to the formula, is 30. The same number works in both directions, which is why people like its symmetry.
Where the Half Your Age Plus 7 Rule Came From
Nobody owns the formula. Versions of it appear in print in the early twentieth century, and it circulated as folk wisdom long before dating apps turned it into a profile cliché. What it is not is a finding of relationship science.
The rule survives because it is easy to compute and roughly matches what societies tolerate: the gap it permits grows with age, which mirrors how most people think about the question. Ease of use and face validity are not the same thing as evidence.
A Common Misunderstanding: the Rule Is Not Research
No study has validated half-your-age-plus-seven as a predictor of relationship success. It is a social norm dressed in arithmetic. Real outcomes depend on the factors every couple faces — communication, shared goals, life stage — none of which the formula measures.
Use it as a conversation starter or a rough social reference point, not as a verdict. Plenty of couples outside its bounds last for decades, and couples comfortably inside it still break up for ordinary reasons.
What the Actual Data Shows Instead
US Census analysis puts the average spousal gap at about 2.2 years, with roughly 40% of married couples having a husband three or more years older. In about 10% of couples, the wife is three or more years older.
Compare that curve with the rule: at typical marriage ages the formula permits gaps far wider than most people actually choose. The data is more conservative than the folk rule — reality clusters near small gaps without needing a formula to get there.
Compute Your Own Gap Instead of Judging It
The age difference calculator gives the exact years, months and days between two birth dates, which is more informative than any single-number rule.
For the fuller picture of what typical gaps look like, see our guide to the normal age gap in relationships.
Enter two birth dates and see the precise age difference in years, months and days.
Get the Exact Gap, Not a Rule of Thumb →Frequently Asked Questions
What is the half your age plus 7 rule?
A folk formula for the youngest acceptable dating partner: divide your age by two and add seven. A 30-year-old gets a floor of 22.
Where does the half your age plus 7 rule come from?
Versions appeared in print in the early twentieth century and it spread as social folk wisdom. It has no scientific origin or validation.
Is the rule scientifically valid?
No. No research links the formula to relationship success. It approximates social tolerance, nothing more.
Does the rule work in reverse as a maximum?
By symmetry, yes: your maximum partner age under the formula is your age minus seven, doubled. It is quoted both ways.
What is the average real-world age gap?
About 2.2 years between US spouses, and half of couples are within two years of each other.
Is dating someone younger than the rule allows wrong?
Between consenting adults, the law cares about age of consent, not folk formulas. The rule is a social reference, not a legal or moral standard.
Why does the permitted gap grow with age?
Because the formula divides your age in half. The same arithmetic that makes it easy is what makes the floor accelerate as you get older.
How exact should an age gap be?
Exact enough to matter for legal and planning purposes. A calculator gives years, months and days rather than rounded years.
Are the dates I enter on this site kept private?
Yes. Everything runs in your browser — nothing is sent to a server and nothing is saved.
Sources
- Wikipedia: Age disparity in sexual relationships
- Pew Research Center: a growing share of US husbands and wives are roughly the same age