What reading age is your patient information? A practical guide to readability scores

Most surgeons have never run a readability score on the leaflet they hand a patient before consent. That is not negligence — it simply is not something clinical training covers. But readability scores are one of the few objective, repeatable measures of whether written information stands a chance of being understood. They are worth knowing, including their limits.

This is a practical guide to the three scores you are most likely to meet — Flesch Reading Ease, Flesch-Kincaid Grade Level and SMOG — what each measures, the reading-age target the NHS sets, the statutory duty behind it in England, and why a score is a starting point, never a verdict.

What a readability score actually measures

Every mainstream readability formula works from the same two ingredients: sentence length and word length. Longer sentences and longer words make a text “harder”; shorter ones make it “easier”. That is essentially all these formulas can see. They do not read for meaning, tone, logical order, or whether the risk a patient most needs appears on page one or page four.

That simplicity is both their strength and their weakness. It makes them fast, cheap and consistent — score the same leaflet twice and you get the same number. It also makes them blind to much of what makes information usable.

Flesch Reading Ease

Flesch Reading Ease returns a number from roughly 0 to 100, where higher means easier. Around 60 to 70 is plain English for a wide adult audience; below 30 is “very difficult”, the territory of academic and legal writing. Because the scale runs counter-intuitively — high means easy — it is often quoted alongside a grade level.

Flesch-Kincaid Grade Level

The Flesch-Kincaid Grade Level reworks the same inputs into a US school grade: a score of 8.0 means the text should be understood by an average student in the eighth grade, around 13 to 14 years old. It is the score built into Microsoft Word, which is why most people have seen it without meaning to. A US grade corresponds, very roughly, to a UK reading age a few years higher — treat the conversion as approximate.

SMOG

SMOG — the Simple Measure of Gobbledygook, published by G. Harry McLaughlin in 1969 — estimates the years of education needed to understand a text, based on the number of long (three-or-more-syllable) words. It is often preferred for health information because it was validated to a stricter comprehension threshold than the Flesch family, and tends to return a slightly harder grade for the same passage. That is a feature: it builds in a margin of safety.

The NHS reading-age target

NHS guidance is clear that patient-facing information should be written for a low reading age — around 9 to 11 years. That is not an insult to patients’ intelligence. Reading age is not IQ or education; it is the level at which someone reads comfortably, and it drops for everyone under stress, in pain, on medication, or newly frightened by a diagnosis — which describes most people reading a surgical consent leaflet.

The gap between that target and reality is well documented. A 2020 retrospective analysis of patient information leaflets and consent forms in Ireland and the UK found that all of them sat above the sixth-grade level recommended for health materials. On plain-English criteria, around half were rated “difficult”, and only about one in fourteen counted as plain English. The point is not to name any one leaflet, but to note that missing the target is the norm, and most authors have no idea by how much.

The Accessible Information Standard: the related legal duty

A related statutory duty sits nearby, and it is worth knowing. The Accessible Information Standard does not mandate a reading-age score directly — it mandates meeting patients’ communication needs — but it is the legal backdrop any leaflet author in England should have in mind. It is published by NHS England as DAPB1605 (formerly DCB1605), under section 250 of the Health and Social Care Act 2012. It requires organisations providing NHS or publicly funded adult social care to identify, record, flag, share, meet and review the information and communication needs of people with a disability, impairment or sensory loss. It is mandatory for those organisations, and it supports compliance with the Equality Act 2010.

Two things matter for anyone writing patient information. First, its scope is communication needs — for example, information in easy-read, large print or braille where a patient needs it — not readability scores as such. A good Flesch score does not by itself discharge the duty; but information built to be accessible from the outset — plain language, an easy-read track, clear structure — is much closer to meeting it than a dense clinical leaflet. Second, a purely private practice may sit outside the strict AIS duty, but not outside its spirit: the Equality Act 2010 applies across the board. Treat the score as one input, not proof of compliance.

Why a score is a starting point, not a verdict

A single number can flatter a bad leaflet and penalise a good one. Because the formulas only count sentence and word length, you can “improve” a score by chopping sentences in half without making the meaning any clearer — and you can be marked down for an unavoidable clinical term the surrounding text defines perfectly well. A leaflet can score beautifully and still bury the one material risk a patient needed to see.

So use the score for what it is good at: a fast, objective flag that a piece of writing is probably too dense and worth a second look. Then judge what the formula cannot see — is every material risk present, does each claim carry a source, is there an easy-read version, does the structure serve someone reading it for the first time in a waiting room? Those are questions of construction, and they are where the real work of accessible patient information lives.

The quickest way to score a leaflet

To see where one of your own leaflets sits, the fastest route is the free Leaflet Stress Test. Paste in the text and it returns the reading age and sentence mix in seconds, alongside a few things a raw score misses — how far down the page the risks first appear, and any claims stated without a source. It costs nothing and stores nothing you paste. It will not tell you your leaflet is good or bad; it will tell you, objectively, where to start looking.

Patient Compass Suite is a clinician-led surgical-pathway suite from GGO Systems. It is a delivery layer for information a clinical team has already approved — not a clinical system — and it holds no patient accounts, and no directly identifying patient information. Founder: Mr Giangiacomo Ollandini, FRCS (Eng), MD, MSc.