Sibling Age Gap Calculator
A simple planning helper for spacing your children. Enter your first child's birth date and either a target age gap or a planned second due date — we'll fill in the rest.
General information for planning, not medical advice.
How it works
Start with your first child's birth date. In "Plan a gap" mode, choose how far apart you'd like the kids to be (years and months) and we estimate the second child's birth date plus a rough conception window to aim for.
Switch to "Compare dates" mode to go the other way: enter a planned or due date for the second baby and see the exact age gap in years and months.
The conception window is a best guess based on a typical 38-week pregnancy. Every pregnancy and family is different, so treat the numbers as a starting point for your own planning.
Frequently asked questions
What's a "good" age gap between siblings? +
There's no single right answer — families do well with gaps from under a year to many years apart. This tool just helps you picture the timing for whatever spacing you have in mind.
How is the conception window worked out? +
We count back about 38 weeks from the estimated second birth date and show a roughly four-week window around that point. It's an estimate for planning, not a fertility prediction.
Does this give medical or fertility advice? +
No. It's a planning helper using simple calendar math. For questions about timing pregnancies, fertility, or your health, talk with your doctor or midwife.
Related reading
- Single vs Double Stroller: Which for Two Kids?Single or double stroller with two children — which actually works better? A neutral comparison of cost, maneuverability, storage and everyday use.Jul 3, 2026 · 4 min readRead more→
- Preparing a Toddler for a New SiblingHow to prepare a toddler for a new baby — when and how to tell them, ways to involve them, and gentle tips for managing the adjustment without guilt.Jun 12, 2026 · 4 min readRead more→
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