The ½-your-age-plus-seven rule explained
The "half plus seven" rule is a popular social heuristic for determining the socially acceptable minimum age of a romantic partner. For the older person, the acceptable youngest partner age is: your age ÷ 2 + 7.
For a 40-year-old: 40 ÷ 2 + 7 = 27. So the socially acceptable range would be 27–66 (the inverse upper bound formula is: (your age − 7) × 2).
This is purely a social rule of thumb, not a scientific measurement of compatibility. Many happy long-term relationships exist well outside this range.
What does research say about age gaps?
- A 2014 Emory University study found that couples with a 1-year age gap had a 3% chance of divorce. Those with a 5-year gap had 18% higher odds, and a 10-year gap raised that to 39%.
- However, the researchers cautioned that age gap alone doesn't cause divorce — shared values, communication, and financial alignment are far stronger predictors of relationship longevity.
- Many cultures and historical periods have had different norms around age gaps. The "half plus seven" rule itself appears to date to the early 20th century in French writing.
How age gap differs by life stage
| Gap Size | Common Characterisation | Generational Difference |
|---|---|---|
| 0–3 years | Same-generation couple | Shared cultural touchstones |
| 4–10 years | Noticeable gap | Different decades, some divergence |
| 11–20 years | Significant gap | Different generational cohorts |
| 20+ years | Large gap | Potentially different life stage priorities |