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Compare two adult ages with the half-your-age-plus-seven rule, reverse boundaries, age gap, and two-way compatibility result.
Last updated: July 20, 2026
Submit two adult ages to see both ranges, the age gap, and whether the informal rule works in both directions.
Enter both adult ages, then select Calculate.
Example: Age 30 and age 28
Guide
The familiar shortcut divides a person's age by two and adds seven. For an age of 30, the arithmetic gives 22. The calculator rounds a fractional result up to the next whole year because a lower boundary of 21.5 is not a practical whole-age answer.
To reverse the rule, subtract seven from the starting age and multiply by two. For someone aged 30, that produces 46. These two operations are algebraic inverses before rounding, so the displayed range is internally consistent even though the social rule itself has no scientific authority.
The saying has circulated as a cultural convention, joke, and rough description of perceived age gaps. It was not created from relationship-outcome research and cannot measure shared values, power differences, life stage, emotional readiness, or whether two people want the same kind of relationship.
No arithmetic rule overrides age-of-consent law, safeguarding duties, workplace or professional boundaries, or the requirement for voluntary consent. The calculator is best treated as a curiosity for adults discussing a well-known phrase—not as permission or advice.
Calculation steps
Step 1
Age 30
Step 2
The familiar shortcut divides a person's age by two and adds seven. For an age of 30, the arithmetic gives 22. The calculator rounds a fractional result up to the next whole year because a lower boundary of 21.5 is not a practical whole-age answer.
Step 3
Lower boundary: Age ÷ 2 + 7, rounded up. Upper boundary: (Age − 7) × 2, rounded down. Minimum input: Both inputs begin at age 18. The calculator does not assess minors' relationships or determine the age of legal consent. Two-way result: Each entered adult is checked against the other person's independently calculated range; this is arithmetic consistency, not relationship approval.
Step 4
Popular-rule range: 22 to 46. 30 ÷ 2 + 7 = 22; (30 − 7) × 2 = 46.
The output reproduces an informal arithmetic saying for two adults and deliberately separates it from law, consent, and relationship advice.
| Assumption | How this page handles it |
|---|---|
| Lower boundary | Age ÷ 2 + 7, rounded up. |
| Upper boundary | (Age − 7) × 2, rounded down. |
| Minimum input | Both inputs begin at age 18. The calculator does not assess minors' relationships or determine the age of legal consent. |
| Two-way result | Each entered adult is checked against the other person's independently calculated range; this is arithmetic consistency, not relationship approval. |
| Input | Output | Why it matters |
|---|---|---|
| Age 30 | Popular-rule range: 22 to 46 | 30 ÷ 2 + 7 = 22; (30 − 7) × 2 = 46. |
| Age 25 | Popular-rule range: 20 to 36 | A half year is rounded upward for the displayed lower boundary. |
| Age 40 | Popular-rule range: 27 to 66 | The widening range illustrates the formula, not a recommendation. |
Edge cases
Do not use folklore arithmetic to assess legality, consent, or safeguarding.
A numerical boundary says nothing about power, dependence, or aligned expectations.
The calculator rounds the minimum upward and maximum downward to whole ages.
Use it to reproduce and compare the informal half-your-age-plus-seven arithmetic rule for two adults and understand how its boundaries are derived.
Do not use folklore as legal, consent, safety, compatibility, or relationship advice, and do not use this calculator for relationships involving minors.
No. It is an informal saying with no legal authority.
Subtracting seven and doubling algebraically reverses halving and adding seven.
No. Health and consent cannot be calculated from ages alone.
It circulated historically as social folklore and changed meaning over time; it is not a research standard.
A displayed age boundary is easier to understand as a completed whole year.
We use these sources to define the age-counting rule, official context, or life-stage assumptions used by this calculator.
Last updated: July 20, 2026
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