Age Difference Calculator
Find the exact age gap between two people
Age Gaps in Relationships
The "half your age plus seven" rule has been the social benchmark for acceptable age gaps since at least the early 1900s. By this formula, a 30-year-old's youngest appropriate partner is 22, a 40-year-old's is 27, and a 50-year-old's is 32. The rule is surprisingly consistent with what research shows about relationship satisfaction — couples within this range report similar levels of satisfaction regardless of the specific gap.
Research from Emory University found that couples with a 5-year age gap are 18% more likely to divorce than same-age couples. At 10 years, the rate increases to 39%. At 20 years, 95%. However, these statistics do not prove that age gaps cause divorce — they likely reflect underlying differences in life stage, values, and social expectations that correlate with larger gaps. Couples who are aware of these challenges and actively address them can thrive at any age difference.
Famous Age Gaps
Throughout history, significant age gaps in relationships have been common among public figures. The key takeaway is not whether age gaps work or do not work — it is that success depends on the individuals involved, their communication skills, and their willingness to navigate the unique challenges that come with being at different life stages. No calculator can measure compatibility. What we can measure is the precise difference between two dates, which is what this tool does.
Age Gaps Between Siblings
For siblings, research suggests different gaps create different dynamics. Siblings 1-2 years apart often develop intense rivalries but also deep bonds through shared experiences. Gaps of 3-4 years tend to produce the most harmonious relationships — the older child is mature enough to not feel threatened, while the younger benefits from a built-in role model. Gaps of 5+ years often result in less rivalry but also less closeness, with the older sibling sometimes filling a quasi-parental role rather than a peer relationship.
What is the half-your-age-plus-seven rule?
Divide the older person's age by 2 and add 7 to find the minimum socially acceptable age of their partner. A 40-year-old: 40/2 + 7 = 27. This is a social guideline, not a rule — healthy relationships can exist outside this range with mutual respect and compatible life goals.
Does age gap affect relationships?
Research shows slightly higher divorce rates for larger gaps, but the effect is modest for gaps under 10 years. The most important factors for relationship success — communication, shared values, emotional intelligence — are unrelated to age. A 5-year gap with strong communication beats a same-age couple with poor communication every time.