Motor & sensory · PRO-ED
PDMS-3 Age Calculator
Chronological age in total months for the Peabody Developmental Motor Scales, Third Edition, with the published age range Birth – 5:11 checked for you.
PDMS-3 at a glance
| Full name | Peabody Developmental Motor Scales, Third Edition |
|---|---|
| Publisher | PRO-ED |
| Published age range | Birth – 5:11 |
| Age format | Total months |
| Corrected age | Corrected age is commonly used for preterm infants until 24 months in physical and occupational therapy evaluation. |
| Discipline | Motor & sensory |
The PDMS-3 measures gross and fine motor development from birth and is a mainstay of paediatric physical and occupational therapy assessment. Motor norms change fast enough in the first two years that prematurity correction routinely changes the conclusion.
How the PDMS-3 wants the age entered
Enter chronological age in total completed months. Entry points for each motor subtest are given by month of age.
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 PDMS-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 PDMS-3 as: 18 months
- 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.
Corrected age and the PDMS-3
Corrected age is commonly used for preterm infants until 24 months in physical and occupational therapy evaluation.
Corrected (adjusted) age is measured from the due date rather than the birth date. Switch the calculator above to Born preterm and enter the gestational age at birth to see both figures side by side. The dedicated adjusted age calculator adds gestational and postmenstrual age, and the corrected age guide explains the convention for families.
Other instruments
Same calculation, different recording format. These are the instruments most often administered alongside the PDMS-3:
| Instrument | Age range | Age format |
|---|---|---|
| Beery VMI | 2:0 – 100:0 | Years;months.days |
| MABC-2 | 3:0 – 16:11 | Years;months |
| Sensory Profile 2 | Birth – 14:11 | Years;months |
| SPM-2 | Birth – 87:0 and older | Years;months |
| WISC-V | 6:0 – 16:11 | Years;months.days |
| WPPSI-IV | 2:6 – 7:7 | Years;months.days |
The full list is on the assessment instrument reference, and the assessment age calculator covers any instrument not listed individually.
PDMS-3, PRO-ED 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.