Consent Form Readability Checker.
Check the reading level of a participant information sheet or consent form against ethics committee targets.
Paste your text to get its Flesch–Kincaid and SMOG grades and reading ease, the hardest sentences and plain language suggestions. The check runs in your browser and your text is never sent or stored.
Sentences and Terms to Review
Hardest sentences
Ranked by their own Flesch–Kincaid grade. Long sentences and words of three or more syllables push the grade up.
Plain language suggestions to consider
Check that each suggestion keeps the meaning in context. This list is not medically reviewed.
Abbreviations to explain
Your text, marked up
- 24 wordsLong sentence, more than 20 words
- termPlain language suggestion
- HeadingNot scored
How to Use the Consent Form Readability Checker
- Paste the text of your participant information sheet and consent form, or use the example. Copy from Word or a PDF: headings, bullet points and line breaks are recognised.
- Choose a target. Grade 8 is the default because the InFORMed template used across Australia asks for it[1]. Switch to grade 6, the AMA recommendation for patient materials[2], or enter your own committee’s target.
- Read the result. The Flesch–Kincaid grade is compared with your target. SMOG sits next to it as the stricter check, with Flesch Reading Ease and the share of long sentences and hard words.
- Work through the review list. Start with the hardest sentences, then the plain language suggestions. Select a suggestion to jump to its first use in the marked up copy of your text.
- Copy or download the report to share with your study team.
The check runs in your browser. Your text is not sent to WeGuide or stored, so you can check a draft before it goes to the ethics committee. Readability is one part of valid consent. Our guide to the four principles of informed consent covers the rest.
What the Scores Mean
Flesch–Kincaid grade level
The US school grade a reader needs, worked out from the average sentence length and the average number of syllables per word. Kincaid and colleagues derived it in 1975 for the US Navy[3]. Most consent form studies report it[4][5][6] and Microsoft Word shows it[2], so committee members can compare results.
SMOG grade
SMOG counts words of three or more syllables. McLaughlin calibrated it on readers who showed complete comprehension of a passage[7], so it usually gives a higher grade: 9.6 against 6.5 for Flesch–Kincaid across 148 patient education materials[8]. A comparison of formulas found SMOG the most consistent and best suited to health care materials[9].
Flesch Reading Ease
A score where higher means easier, usually between 0 and 100. Scores below 60 count as difficult[10]. Flesch named seven bands, from 90 to 100 at the easy end to below 30 at the difficult end[11].
Other formulas
Gunning Fog, Coleman–Liau and the Automated Readability Index appear under All formulas, with the range and median of all five grades. They are kept out of the headline because formulas can disagree by up to 5 grades on the same text[9], and a wall of scores invites picking the lowest.
The Formulas Used Here
W is words, S sentences, Y syllables and P words of three or more syllables.
Flesch–Kincaid grade = 0.39 × (W ÷ S) + 11.8 × (Y ÷ W) − 15.59
SMOG grade = 1.0430 × √(P × 30 ÷ S) + 3.1291
Flesch Reading Ease = 206.835 − 1.015 × (W ÷ S) − 84.6 × (Y ÷ W)
The Flesch–Kincaid constants come from the 1975 Navy report[3] and SMOG uses equation (d) of McLaughlin’s 1969 paper[7], both read in the original. McLaughlin counted polysyllables in 30 sentences. Here every sentence is used and the count is scaled to 30 sentences, the method the NCI gives for texts shorter than 30 sentences[12]. Below 30 sentences SMOG is marked as less reliable. The Flesch Reading Ease constants come from a secondary source, DuBay’s review of readability research[11], because the 1948 paper[13] was not available to read.
Gunning Fog = 0.4 × (W ÷ S + 100 × complex words ÷ W)
Coleman–Liau = 0.0588 × letters per 100 words − 0.296 × sentences per 100 words − 15.8
ARI = 4.71 × (characters ÷ W) + 0.5 × (W ÷ S) − 21.43
The Fog constants are as reproduced by DuBay[11][14] and the Coleman–Liau constants are multiplied out from the published two step form[15], so both come from secondary sources. The ARI constants come from the 1967 report[16].
How Sentences, Words and Syllables Are Counted
- Headings. A short line of up to 12 words without a full stop is treated as a heading and skipped. McLaughlin counted only strings ending in a full stop, question mark or exclamation mark as sentences[7].
- Bullet points. Each item counts as a sentence, as the Kincaid counting instructions do for list items[3].
- Abbreviations with full stops. Dr., e.g. and a.m. do not end a sentence. Software that ends a sentence at every full stop reports lower grades[2].
- Numbers and abbreviations are counted as read aloud, so $300 is three hundred dollars and ECG is three syllables. The Kincaid instructions count symbols and figures the way they are pronounced[3]. Both settings can be switched off under Advanced options.
- Contact details. Phone numbers, email and web addresses and reference codes count as one short word, so a contacts paragraph does not inflate the grade.
- Syllables. Words listed in the CMU Pronouncing Dictionary use its count[17]. Other words, including many medical terms and Australian spellings such as haematoma, use rules. In our testing against the NCI dictionary’s pronunciation guides for 2,216 cancer terms missing from the CMU dictionary, the rules gave the exact count for an estimated 95% to 97% of terms and were within one syllable for more than 99.9%[18].
Where the word list comes from
The plain language suggestions draw on plainlanguage.gov[19] and the CDC’s Everyday Words list[20], and on our own wording with meanings checked against the NCI Dictionary of Cancer Terms[18]. Each suggestion shows its source.
Reading Level Targets for Consent Forms
Regulations ask for language participants can understand, without a number[21]. ICH E6(R3) asks for information that is clear and concise and uses simple language[22]. Numeric targets come from guidance, and a Flesch Reading Ease below 60 is described as difficult[10].
Australia: grade 8
The InFORMed participant information and consent form guide says to aim for grade 8, adjusted for your audience, with sentences of 20 words or fewer[1]. NHMRC endorses the template, and Australian jurisdictions endorsed it under National Mutual Acceptance in December 2025[23]. The 2025 National Statement asks for information presented in ways suitable to each participant[24].
AMA: grade 6 or lower
The AMA Foundation manual for clinicians recommends writing patient materials at or below grade 6, and lower for practices where many patients have limited literacy[2]. The Australian Government Style Manual says writing to a year 7 level makes content usable for most people[25].
US IRBs: grade 5 to 10
Of 114 US medical school IRB websites, 61 published a readability standard, from grade 5 to grade 10. The template text on those sites averaged grade 10.6, 2.8 grades above the IRBs’ own standards[5]. Enter your IRB’s grade as your own target.
UK HRA: no grade
The HRA asks for sentences of about 20 words, no more than 2 hard words per sentence, and information no harder to read than a medicines leaflet or a tabloid newspaper[26]. Its design principles point to tools such as Flesch–Kincaid and SMOG, and ask for testing through public involvement as well[27].
Consent Forms Are Usually Written Above Target
Studies in Australia, the UK, the US and Europe find the same pattern.
- 248 Australian interventional information sheets averaged Flesch–Kincaid grade 11.4 and SMOG 13.2, with a median of 3,848 words. Only 3 met grade 8[6].
- 40 anaesthesia research information sheets from Australia and New Zealand averaged SMOG 12.9 and Flesch–Kincaid 11.9[28].
- 522 UK mental health participant information sheets averaged grade 9.8 and grew longer over time[29].
- 112 oncology trial consent forms averaged grade 9.8, and fewer than 15% met grade 8[30]. In 137 earlier oncology forms, 6% met grade 8[4].
- Consent documents for 4 COVID-19 vaccine trials averaged 8,333 words, about 35 minutes of reading, and all were above grade 9[10].
- 67 phase 3 trials in the EU clinical trials database had information sheets with a median of 16 pages and 5,746 words[31].
Readers vary as well. About 44% of Australian adults read at literacy level 1 or 2[25], and in the 2003 US national assessment 36% of adults had basic or below basic health literacy[32].
Does Simpler Text Improve Understanding?
Simpler forms help, but readable text alone is not enough.
- A review of 54 interventions tested in randomised trials found that redesigned consent forms, with plainer language, clearer layout or graphics, improved understanding without lowering satisfaction or enrolment[33].
- In a randomised trial of 150 people, a simplified form improved understanding regardless of health literacy[34].
- A grade 7 form was preferred to a grade 16 form and found easier to read, but comprehension was similar, 58% against 56%[35]. An easy to read statement lowered anxiety without changing comprehension or accrual[36].
- A form with 63% fewer words gave the same comprehension as the standard form[37].
- Across 103 studies, participants understood randomisation 52.1% of the time and their freedom to withdraw 75.8% of the time, with no improvement over 30 years[38]. In an earlier review, talking one to one was the most effective way to improve understanding[39].
A score on target is not proof of understanding. Treat the grade as a screening check, then test the information with people like your participants.
How to Write a Clearer Information Sheet
- Put the key information first. The US Common Rule requires consent to begin with a concise and focused presentation of the key information[21].
- Keep sentences to 20 words or fewer and paragraphs to 2 or 3 sentences[1]. Split sentences that string ideas together with and, which or that.
- Use short, familiar words, with no more than 2 hard words in one sentence[26]. Keep terms participants need, such as placebo, and explain each one once.
- Explain every abbreviation the first time you use it[40]. The checker lists the ones it could not find explained.
- Cut what participants do not need. A rewrite of the COVID-19 vaccine consent documents under 3,000 words at grade 7 to 8 was possible[10].
- Test it with people. The HRA asks researchers to test information through public involvement as well as with readability tools[27].
When the form moves online, our guides to eConsent in clinical trials and eConsent best practices cover how to present it on screen. WeGuide eConsent keeps each approved version of the form with a full audit trail.
Limitations of Readability Formulas
- They count only word and sentence length. They cannot judge order, layout, pictures or whether a word is familiar to your readers[41][42].
- Formulas can give grades up to 5 levels apart on the same text, and one formula can vary by up to 6 grades with the sample, formatting and software[9].
- SMOG has a standard error of about 1.5 grades[7], so a one grade change between drafts may not be real.
- A string of nonsense words still gets a grade[2].
- The NCI passes on three principles: use formulas only with other assessment, only for readers like those a formula was validated on, and never write to the formula[12].
- This checker is built for English text. Check translated versions with readers of that language.
- The plain language suggestions are a starting point, not a medically reviewed glossary. Check that every change keeps the meaning.
Participants also need information at the right time, not only at enrolment. Our patient education module delivers it during the study.
Moving consent to digital?
WeGuide eConsent delivers your approved information sheet and consent form in the participant’s app, with electronic signatures, version control and a full audit trail. Education content can follow at set points in the study, in the participant’s language.
Frequently Asked Questions
Answers about reading levels, readability formulas and writing consent information that participants can understand.
Have another question?What reading level should a participant information sheet be?
Aim for grade 8 in Australia, where the NHMRC endorsed InFORMed guide recommends grade 8, adjusted for your audience. The AMA recommends grade 6 or lower for patient materials. US IRBs set their own targets, and in one study the 61 IRBs that published a standard ranged from grade 5 to grade 10. The UK HRA sets no grade but asks for sentences of about 20 words.
Which readability score should I use?
Use Flesch–Kincaid to compare your text with your committee’s target, because most guidance and consent form studies use it. Then check SMOG, which estimates the grade needed for full comprehension and usually gives a higher grade. A Flesch Reading Ease of 60 or more is a useful extra check. Do not choose whichever formula gives the lowest grade.
Why is my score different from Microsoft Word or another checker?
Tools count sentences, syllables, numbers and headings differently, and formulas can differ by up to 5 grades on the same text. This checker skips headings, keeps abbreviations such as Dr. inside a sentence, reads numbers and abbreviations aloud, and uses a pronouncing dictionary plus rules for medical terms and Australian spellings. Advanced options let you count numbers and abbreviations as one syllable each.
Does a low grade level mean participants will understand the form?
No. Simpler forms are preferred and cause less anxiety, and redesigned forms improved understanding in a review of randomised trials, but in some trials comprehension did not change. A readability score measures only word and sentence length. Test the information with people like your participants and talk it through with each person who considers taking part.
Is my consent form text sent to WeGuide?
No. The check runs in your browser, and your text is not uploaded, sent to WeGuide or stored by the tool. When you first use the checker, the page loads one extra file, a syllable dictionary, and nothing about your text goes with that request. Close or reload the page and the text is gone.
How are headings, bullet points and numbers counted?
A short line of up to 12 words without a full stop is treated as a heading and skipped. Each bullet point counts as a sentence. Numbers are counted as they are read aloud, so $300 is three hundred dollars, and abbreviations letter by letter, so ECG is three syllables. You can change both settings under Advanced options.
What counts as a long sentence or a hard word?
A long sentence has more than 20 words, the limit that both the InFORMed guide and the UK HRA suggest. A hard word has three or more syllables, not counting numbers and abbreviations. The HRA suggests no more than two hard words in one sentence, and the checker counts the sentences that have more than that.
Should I replace every medical term?
No. Keep the terms participants need, such as placebo, and explain each one once in plain words. Replace terms that have an everyday equivalent, and explain every abbreviation the first time you use it. The suggestions in this tool are a starting point, not a medically reviewed list, so check that each change keeps the meaning.
Why is the SMOG grade higher than Flesch–Kincaid?
SMOG was calibrated on readers who showed complete comprehension of a passage. Flesch–Kincaid was calibrated so that half of the readers at a grade scored at least 35% on a fill in the gap test, a lower bar. SMOG therefore usually gives a higher grade, for example 13.2 against 11.4 in a review of 248 Australian information sheets.
How long should a consent form be?
No rule sets a length, but shorter is usually easier for participants. The US Common Rule requires consent to begin with the key information, and in one trial a form with 63% fewer words gave the same comprehension as the standard form. In a review of Australian information sheets, the median length was 3,848 words.
Related Research Tools
Free tools for planning and running clinical research, built on published methods.
References
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Licence notice
Copyright (C) 1993-2008 Carnegie Mellon University. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. The contents of this file are deemed to be source code. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY “AS IS” AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- National Cancer Institute. NCI Dictionary of Cancer Terms and its pronunciation guides, glossary API. Credit: National Cancer Institute. cancer.gov
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Formulas, counting rules and all 91 reference vectors (27 texts, 56 words and 8 formulas) checked on 20 October 2026 by the WeGuide editorial team. The plain language suggestions have not been medically reviewed. This tool is for research planning and education. It is not a medical device and does not give medical or legal advice.
