ToolPorch / Scaled Score to Percentile
Scaled Score to Percentile Calculator
Convert a subtest scaled score (mean 10, SD 3 — the metric WISC-V, WAIS-IV, WPPSI-IV, CELF-5, and NEPSY-II subtests report in) to a percentile rank, either direction. For composite/index scores on the M=100 metric, use the full standard, scaled, T & z-score converter.
Scaled score reference table
Scaled scores conventionally run 1–19. Here's the full range against its percentile and standard-score equivalent:
| Scaled | Standard equiv. | Percentile | Common label |
|---|---|---|---|
| 19 | 145 | >99 | Very superior |
| 16 | 130 | 98 | Very superior |
| 13 | 115 | 84 | High average |
| 10 | 100 | 50 | Average |
| 8 | 90 | 25 | Average |
| 7 | 85 | 16 | Low average |
| 4 | 70 | 2 | Below average |
| 1 | 55 | <1 | Well below average |
Frequently asked questions
Why do subtests use scaled scores instead of standard scores?
Composite/index scores (Full Scale IQ, Verbal Comprehension, etc.) use the standard-score metric (M=100, SD=15) because they combine several subtests. The individual subtests that feed a composite report on the narrower scaled-score metric (M=10, SD=3) so a 15-point spread doesn't make single-subtest variation look bigger than it is. Same normal curve, different ruler.
What counts as a good scaled score?
Scaled scores run roughly 1–19. 8–12 is the average band (25th–75th percentile). 13–15 is high average, 16+ is superior. 5–7 is low average, below 4 is well below average — publishers' exact labels vary, so match the label system of the test you're reporting.
Can I add scaled scores to get a composite?
Not by simple averaging into a standard score without the test's own conversion table — composites are usually the sum of scaled scores run through a norm table, not (sum × 15/3 + 100). Use this converter for reading one subtest's percentile, not for hand-deriving an index score.
How is the percentile calculated?
Your scaled score is converted to a z-score (z = (score − 10) ÷ 3), and the percentile is the area of the standard normal curve below that z — the same theoretical model publishers use to build their norm tables.
Is anything I enter stored?
No. All conversion happens in your browser; nothing is transmitted or saved.