The Fry Graph
Using a Fry Graph is one way of checking reading age. It is a simple graph that measures language across two basic parameters; syllables and sentences. The assumption is that writing that contains shorter sentences and words with a lower number of syllables is easier to read. Conversely, writing with longer sentences and more syllables per word is more challenging.
To make a calculation using Fry, simply take a sample of the text of 100 words. Ensure the sample is representative of the rest of the text, and avoid including headings, captions and other additional pieces of text. It does not matter if the sample is from the beginning, middle or end of the piece.
Next, count up how many sentences are in the piece of writing. Estimate what percentage of the sentence is left over if the 100 word sample does not divide neatly into an exact number of sentences (it rarely will). For example, you may find there are 4.8 sentences per 100 words in your sample.
Then, count how many syllables are in the sample. This is often easier to do if you use a pencil to note the total at the end of each line so you don't lose your place. There is nothing more frustrating than counting syllables to the ninetieth word, then forgetting what you are up to!
Use the Fry graph (which has sentence number on the Y axis and syllables on the X axis) to find the reading age of the text. For example, a passage with around four sentences per 100 words and 120 syllables in the same passage will have a reading age of 12 years. A passage with only 3 sentences per 100, and 144 syllables will have a reading age of about 15 years. Note that some versions of the graph show age in years, while others show grade level. Check which version you are using!
For greater accuracy, repeat the calculations using three samples of writing from the text. That means you will calculate the score based on 3 x 100 word samples.