SMOG Calculator

Online SMOG calculator which you can use to calculate the readability index for readability level of your own documents or texts from a website.

Using the SMOG Calculator

The easiest way to establish the readability level of a text is to use the SMOG calculator developed by Harry McLaughlin PH.D.

There is an alternative method you can use to determine the reading level of your written materials. This method is especially useful when you are revising existing patient/family education materials and may not have access to the original Microsoft Word document.

Word Counting Rules:

• A sentence is any string or words ending in a period, exclamation point or question mark.
• Words with hyphens count as one word.
• Proper nouns are counted.
• Read numbers out loud to decide the number of syllables.
• In long sentences with colons or semicolons followed by a list, count each part of the list with the beginning phrase of the sentence as an individual sentence.
• Count abbreviations as if they were not abbreviated.
• Do not count verbs ending in 'ed' or 'es' that make the word have a third syllable.

SMOG for Shorter Passages (<30 sentences)

Use this formula and SMOG Conversion Table II for material containing less than 30 sentences, but no less than 10 sentences.

• Count the total number of sentences in the material.
• Count the number of words with 3 or more syllables.
• Find the total number of sentences and the corresponding conversion number in SMOG Conversion Table II.
• Multiply the total number of words with 3 or more syllables by the conversion number. Use this number as the word count to find the correct grade level from Table I.