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What The Age Gap Calculator Works Out
- Age gap: the difference between the two birth dates in whole years and months, plus the exact number of days apart. The gap is fixed in days but shifting in feel: the same five years that spans school years and life stages at 15 and 20 is barely visible at 45 and 50, which is why perceived gaps shrink with age.
- Current ages: both people's ages in completed years today. Population data says most couples cluster close together: the average age gap in UK couples sits around 2 to 3 years, and gaps above 10 years cover under one couple in ten.
- Fun fact: how far into life the older person was when the younger was born, or a note that the two are within a year of each other.
- Ages as of (advanced): work out both ages on any date, past or future, instead of today.
- Half-your-age-plus-seven rule (advanced): the Victorian-era folk guideline for the socially accepted youngest partner. A 40-year-old's floor comes out at 27; the same rule read the other way gives the younger partner's ceiling at (age minus 7) times 2. The card says whether the pair passes today and, if not, the age at which it would. It is a parlour rule, not advice.
- Younger person's age then (advanced): enter an age for the older person and see how old the younger was on that birthday, or how long after it they were born. Handy for the "when you were 18, I was still at primary school" conversation.
- Same school year (advanced): whether the two birthdays fall in the same school cohort. In England and Wales the cut-off is 1 September, in Scotland roughly 1 March and in Northern Ireland 2 July, so two children 11 months apart can share a classroom or sit a year apart depending which side of the date they fall. The sub-line gives the September each cohort would typically start school.
- Older was twice as old on (advanced): the one date when the older person's age was exactly double the younger's, which happens when the younger has been alive for as many days as separate the two births. The ratio only ever shrinks after that.
- Milestone table (advanced): the younger person's age on each of the older person's landmark birthdays from 18 to 90, with the dates, useful for siblings, couples and the parlour-game comparisons between celebrities and historical figures.