Behavior & adaptive · WPS

ABAS-3 Age Calculator

Chronological age in years;months for the Adaptive Behavior Assessment System, Third Edition, with the published age range Birth – 89:11 checked for you.

Birth Date

Test / Assessment Date

ABAS-3 at a glance

Full name	Adaptive Behavior Assessment System, Third Edition
Publisher	WPS
Published age range	Birth – 89:11
Age format	Years;months
Corrected age	Not applied in standard scoring.
Discipline	Behavior & adaptive

The ABAS-3 is a rating-scale measure of adaptive skills across conceptual, social and practical domains, available in parent, teacher and self-report forms. Issuing the wrong form for the age is a common and easily avoided error.

How the ABAS-3 wants the age entered

Record chronological age as years;months. The age also determines which rating form is issued (infant, preschool, school, adult).

The underlying calculation is the same for every instrument — complete years, complete months, then the leftover days. What differs is which part of it goes on the form. The calculator above reports all four figures at once, so you can copy the one the ABAS-3 manual asks for without recalculating:

Years;months.days — the full record-form format, e.g. 1;6.20
Years;months — complete units only, e.g. 1;6
Complete months — e.g. 18 months
Rounded to nearest month — e.g. 19 months (1;7), using the 15-day threshold

The exact date arithmetic, including month-end clamping and leap-day handling, is documented in the calculation methodology.

Worked example

A child born February 26, 2025 and assessed on September 15, 2026:

Chronological age: 1 year, 6 months, 20 days
Record on the ABAS-3 as: 1;6
Day remainder: 20 days — 15 or more, so a nearest-month rounding rounds up

Enter these exact dates above to reproduce the result. Every figure on this page is computed by the same library that runs the calculator, so the worked example and the tool can never disagree.

Other instruments

Same calculation, different recording format. These are the instruments most often administered alongside the ABAS-3:

Instrument	Age range	Age format
Vineland-3	Birth – 90:11	Years;months.days
BASC-3	2:0 – 21:11 (self-report 6:0 – 25:11)	Years;months
Conners 4	6:0 – 18:11	Years;months
WISC-V	6:0 – 16:11	Years;months.days
WPPSI-IV	2:6 – 7:7	Years;months.days
WAIS-5	16:0 – 90:11	Years;months.days

The full list is on the assessment instrument reference, and the assessment age calculator covers any instrument not listed individually.

Checked against the documented calculation method and its automated test suiteLast reviewed July 26, 2026Who publishes this

ABAS-3, WPS are trademarks of their respective owners. AgeCalc is not affiliated with, endorsed by, or sponsored by any of them. Brand names are used descriptively to identify the assessment formats this calculator supports.

Frequently Asked Questions

Subtract the date of birth from the test date to get complete years, complete months, and the leftover days. For the ABAS-3 the age is recorded as years;months. Record chronological age as complete years and complete months (e.g. 10;11). The day remainder is not carried onto the form. A child born February 26, 2025 and tested on September 15, 2026 is 1;6.20 — 1 year, 6 months, 20 days.

WPS publishes the Adaptive Behavior Assessment System, Third Edition for ages Birth – 89:11. Outside that range the instrument has no norms, so a score cannot be computed even though the chronological age can. Always confirm the range in the edition of the manual you are scoring from — publishers revise ranges between editions.

No. For the ABAS-3 the partial month is not rounded up — record complete years and complete months, and report the leftover days separately where the form has a place for them. Rounding up moves the examinee into the next norm band and changes the standard score.

Prematurity correction is not part of standard ABAS-3 scoring — use chronological age from the date of birth. If a clinical team decides to report a corrected age alongside it for context, say so explicitly in the report so the score is not misread.

Standardized scores are read from age-banded norms. A one-month error can move an examinee into a neighbouring band and shift a standard score by several points — enough to change an eligibility decision at a cut-off. Recomputing the age from the birth date and test date, rather than reusing an age from an earlier report, is the reliable check.