WISC-V, WAIS-IV & KTEA Age-Band Rounding Rules Explained

July 14, 2026

Why Age Bands Exist

Norm-referenced tests like the WISC-V, WAIS-IV, and KTEA-3 don’t score a raw total against one master table. They score it against a table built for a narrow age band — often just a few months wide. The examinee’s exact chronological age on the test date decides which row of that table applies. Get the age wrong by even a few days near a boundary, and the standard score, percentile rank, and eligibility conclusion can all shift. Use the chronological age calculator to get that exact figure instantly instead of doing calendar subtraction by hand.

The Rounding Rule Most Pearson Manuals Use

For WISC-V, WAIS-IV, and KTEA-3, chronological age is first computed as an exact years/months/days figure using calendar subtraction, then rounded to the nearest month with a fixed threshold:

Remainder of 16 days or more rounds the month up
Remainder of 15 days or fewer rounds the month down (stays as-is)

Worked example: A child was born April 20, 2015, and is tested July 14, 2026.

Exact age    = 11 years, 2 months, 24 days
24 ≥ 16  →  round the month up
Test age     = 11 years, 3 months  →  reported as "11:3"

That single-day threshold is not cosmetic. A test-taker with a 15-day remainder and one with a 16-day remainder can land in different age bands on the same norm table, even though only one day separates their exact ages.

Not All Pearson Instruments Round the Same Way

This is the part examiners most often get wrong: the 16-day rounding rule is not universal across every Pearson product. Pearson’s own assessment support documentation, covering test-date age calculation for a separate set of instruments, states plainly that for those calculations “all months are assumed to have 30 days” and that “ages are not rounded up to the next month or year” at all — a flat, non-rounding convention that produces a different result than the WISC-V/WAIS-IV/KTEA-3 method.

Convention	How it works	Used by
16-day rounding (standard)	Exact age computed, then rounded to nearest month using a 15/16-day threshold	WISC-V, WAIS-IV, KTEA-3
Flat 30-day month, no rounding	Every month treated as exactly 30 days; remainder days are kept, never rounded	Certain other Pearson-administered calculations — confirm per instrument

The practical takeaway: never assume “it’s a Pearson test, so it must use the 16-day rule.” Confirm the exact method in the administration manual for the specific edition you’re using, since conventions differ between instruments and have changed between older and newer editions of the same test family.

How the Calendar-Subtraction Step Works First

Before any rounding happens, the exact age has to be computed correctly using calendar subtraction with borrowing — not a shortcut like dividing total days by 365.25, which produces a decimal age that doesn’t map cleanly onto a Y:M:D norm table row. The subtraction borrows days from the calendar month immediately before the test month when the test day is smaller than the birth day, and borrows a year when the resulting month count goes negative. See common mistakes when calculating test age for the specific ways examiners get this step wrong, including the decimal-approximation trap.

Quick Reference Table

Test	Age format required	Rounding convention
WISC-V	Years:Months (rounded)	16-day threshold, round up
WAIS-IV	Years:Months (rounded)	16-day threshold, round up
KTEA-3	Years:Months (rounded)	16-day threshold, round up
Other Pearson instruments	Varies	Confirm manual — some use flat 30-day months with no rounding

Why This Matters for Documentation

Special education assessment guidance echoes the same principle: age must be calculated consistently and precisely because a miscalculated age can pull the wrong norm-table row and produce an inaccurate standard score. This is exactly why examiners are trained to recompute age directly from the birth date and test date every time, rather than copying a prior report’s age forward or eyeballing a difference on a calendar.

For a full set of worked examples showing exact age alongside the rounded test age band — including the precise point where a single day flips the rounding outcome — see chronological age calculation examples for WISC-V, WAIS-IV & KTEA. And if the examinee was born prematurely, the rounding rule above still applies to raw chronological age — but you may also need corrected age for premature infants for certain early-childhood instruments.

Always calculate directly from the birth date and test date with the chronological age calculator, then apply the rounding convention specified in your test’s current administration manual.