Several tools have been developed that measure the quantitative dimension of text complexity. Below is a list of the tools:
ATOS by Renaissance Learning
This tool uses two formulas: ATOS for Text and ATOS for Books. Both formulas consider words per sentence, average grade level of words and characters per word.
Degrees of Reading Power (DRP) by Questar Assessment, Inc.
This tool measures word length, sentence length and word familiarity. The DRP Scale goes from 0 to 100 with higher values meaning more difficult text. Students' reading ability and the readability of text are reported on the same scale.
This formula considers two factors: words and sentences. It uses word and sentence length to predict semantic and syntactic complexity.
The Lexile Framework for Reading by MetaMetrics
A Lexile measure represents both the complexity of text and an individual's reading ability. These measures are expressed by a number followed by an L (for example, 950L). Lexile measures are reported in WV on the WESTEST2 report for each child.
Reading Maturity by Pearson Education
This tool uses Latent Semantic Analysis (LSA) to measure how much language experience is required to achieve the meaning of each word, sentence and paragraph in a text.
SourceRater by Educational Testing Service
This tool uses a variety of natural language processing techniques to glean information about syntactic complexity, vocabulary difficulty, paragraph structure and five other dimensions.
Easability Indicator by Coh-Metrix
This program was developed at the University of Memphis and Arizona State University. It analyzes text based on narrativity, syntactic simplicity, word concreteness, referential cohesion and deep cohesion.