Readability - testing how easy a text is to read

SMOG (simplified measure of gobbledygook) is a formula that gives a readability level for written material. Readability is an attempt to match the reading level of written material to the "reading with understanding" level of the reader.

The easiest way to establish the readability level of a text is to use an online SMOG calculator. In Spring 2009, NIACE made a new calculator available via its website at www.niace.org.uk/development-research/readability that can be used to calculate the readability level of any text that is pasted into it. This is based on research into different readability tests commissioned by NIACE and carried out by Professor Colin Harrison at Nottingham University.

There is also a manual method you can follow to calculate a SMOG level on longer texts such as books. This has been used extensively as one of a range of criteria for identifying accessible books for less confident adult readers - see www.firstchoicebooks.org.uk for more than 600 titles, including the Quick Reads, which have been selected according to these criteria.

To get an accurate SMOG level for a long piece of text, most methods recommend taking at least three samples - for example, one each from the beginning, middle and end - and taking the average of the three scores.

All the readability tests rely on a very rough gauge of the level of reading vocabulary people can expect to acquire by a certain point in their development - they stop generally around the 20 mark. But successful reading is about far more than word recognition - it's about style, content, physical presentation, complexity of intellectual engagement required, learner interest, confidence and skill. Advice on presentation of text

Relating SMOG levels to adult literacy levels

There are no simple answers about relating readability levels to adult literacy levels - they don't equate exactly and are not meant to. SMOG is a measure of readability and not the reading age of a text. The formula was developed to help librarians categorise their stock more easily for learners and practitioners and to act as an indication of level of difficulty, but the adult literacy standards were designed to indicate what specific skills functioned at particular levels, unrelated to age.

It would be impossible to produce materials that solely met the standard definitions at each level. As a rough indication, SMOG 9-10 = Entry Level 3, 11-12 = Level 1 and 13-14 = Level 2 but that it's far from an exact science and SMOG should only be taken as one indicator among many for the suitability of a text. Equating SMOG levels with reading ages is too simplistic. Adult literacy levels - what do they mean?

Calculating the SMOG level of a text

1. Select a page of a book

2. Count 10 sentences

3. Count the number of words which have three or more syllables

4. Multiply this by 3

5. Circle the number closest to your answer

7. Find the square root of the number you circled

8. Add 8 = Readability level

Most people will understand a readability level under about 10.

Analysis undertaken by Niace has shown average scores for newspaper editorials as follows:
The Sun: under 14
The Daily Express: under 16
The Telegraph and The Guardian: over 17
More information is at www.niace.org.uk/development-research/readability

NB The original SMOG formula gave a score related to US school grade levels. In this version, the constant added at the end has been changed from 3 to 8, to give a readability level.