In early intervention, exact age is the foundation of every eligibility decision — and for preterm infants, it's the chronological age you then correct for prematurity. This free calculator gives you that precise years;months;days, fast.
Why exact age is the eligibility hinge
Under IDEA Part C, eligibility is decided against age-normed instruments and, in many states, a percent-delay threshold. Both depend on an exact age. The youngest children have the narrowest bands, so a few days off can flip a determination. Publisher scoring uses the borrow-30 method (every month = 30 days), not ordinary calendar math.
Instruments this matters for
- Bayley-4 — Bayley Scales of Infant & Toddler Development
- DAYC-2 — Developmental Assessment of Young Children
- BDI-3 — Battelle Developmental Inventory
- State Part C eligibility tools and percent-delay worksheets
What this tool gives you
- Exact years;months;days in borrow-30 format
- Settable birth and test dates, recalculated as you change them
- Deterministic, unit-tested math; 100% private — nothing you enter leaves your device
Why not a generic calculator or AI? They give calendar age, not the borrow-30 result — here's the difference →
Built for your assessments
- Speech-Language Pathologists
- School Psychologists
- Pediatric OTs & PTs
- Early Intervention
Get the exact chronological age — free.
Free iOS / Mac app, or use it in your browser. No ads, no accounts, no subscription.
