How do I know what type of IBS I have?

Count your stools by Bristol type on days when at least one bowel movement was abnormal. More than 25% hard and less than 25% loose is IBS-C, the reverse is IBS-D, more than 25% of both is IBS-M, and anything else is IBS-U.

What is the difference between IBS-C and IBS-D?

Only stool form. IBS-C means hard or lumpy stools (Bristol 1 to 2) make up more than a quarter of bowel movements on abnormal days and loose stools less than a quarter. IBS-D is the exact reverse.

What does IBS-M mean?

IBS with mixed bowel habits. More than 25% of your bowel movements on abnormal days are hard and more than 25% are loose. It is a defined subtype, not a sign that a clinician could not decide.

IBS unclassified. You meet the criteria for IBS, but your stool forms do not reach the thresholds for IBS-C, IBS-D or IBS-M. It often changes once more days are logged.

Do normal bowel movements count when working out my IBS type?

Under Rome IV, only days with at least one abnormal bowel movement count. Days when every stool was normal are left out of the sum entirely, which is the main change from Rome III.

Can laxatives or Imodium change my IBS subtype?

Yes. Rome IV says a subtype can only be confidently established when you are not taking medicines used to treat bowel habit. Tell your clinician what you were taking while you logged, and do not stop a prescribed medicine without asking them.

Can your IBS type change over time?

Yes, and it usually does. In a year-long diary study, more than 75% of women with IBS changed subtype at least once, though only 29% swung between IBS-D and IBS-C.

Is it better to work out my IBS type from memory or a diary?

A diary. In one study, recalled and diary-recorded subtypes agreed in only 54% of people, and only the diary version tracked how fast the gut was actually moving.

IBS Type Calculator: IBS-C, IBS-D or IBS-M?

Work out your Rome IV IBS subtype from your Bristol stool counts.

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Updated October 3, 2026

The short answer

Your IBS type is set by stool form alone, counted only on days when at least one bowel movement was not normal. Under Rome IV, IBS-C means more than 25% of those bowel movements were Bristol type 1 or 2 (hard or lumpy) and less than 25% were type 6 or 7 (loose or watery). IBS-D is the reverse. More than 25% of both is IBS-M. If neither reaches 25%, it is IBS-U.

Where are your numbers coming from?A stool diary over about two weeks is the most reliable source.

On your abnormal days, how many bowel movements were hard or lumpy?Bristol type 1 (separate hard lumps) or type 2 (lumpy sausage). Only count days when at least one bowel movement was not normal.

bowel movements

On those same days, how many were loose or watery?Bristol type 6 (mushy, fluffy pieces) or type 7 (entirely liquid).

bowel movements

On those same days, how many were in between?Bristol type 3, 4 or 5. Leave at 0 if you only kept track of abnormal stools, for example by thinking back over your last 10 that were not normal.

bowel movements

Were you taking anything for your bowels during that stretch?Rome IV subtyping assumes you are not on medicines that change stool form.

How to use the IBS Type Calculator

1Log every bowel movement for about two weeks with its Bristol stool type, or think back over your last 10 that were not normal.
2Keep only the days when at least one bowel movement was abnormal, and count how many on those days were hard (types 1 to 2), loose (types 6 to 7) and in between (types 3 to 5).
3Tell the calculator whether you were taking a laxative or an antidiarrhoeal, since both change stool form.
4Get your Rome IV subtype, the percentages behind it and what to read next.

The Rome IV rule for IBS subtypes

Rome IV, the criteria gastroenterologists use worldwide, splits IBS into four subtypes by the predominant stool form. Pain, bloating, urgency and how often you go are not part of the calculation.

Since Rome IV, the percentages are worked out only across days with abnormal bowel movements. Under Rome III every bowel movement counted, which left many people with intermittent symptoms in the unclassified group.

Subtype	Hard stools (Bristol 1 to 2)	Loose stools (Bristol 6 to 7)
IBS-C, constipation	More than 25%	Less than 25%
IBS-D, diarrhoea	Less than 25%	More than 25%
IBS-M, mixed	More than 25%	More than 25%
IBS-U, unclassified	Meets IBS criteria but fits none of the above

The Bristol stool types in plain words

The Bristol Stool Form Scale was developed as a guide to how fast stool moves through the gut: hard types tend to come with slow transit and loose types with fast transit. That is why stool form, rather than frequency, decides the subtype.

Type	Looks like	Counts as
1	Separate hard lumps, like nuts	Hard
2	Sausage-shaped but lumpy	Hard
3	Sausage with cracks on the surface	In between
4	Smooth, soft sausage or snake	In between
5	Soft blobs with clear-cut edges	In between
6	Fluffy, mushy pieces with ragged edges	Loose
7	Watery, no solid pieces	Loose

Why your subtype can change

Subtypes are not fixed. In a year of diary records from 317 women with IBS, more than 75% moved into another subtype at least once, most often between IBS-M and IBS-C, and only 29% swung between IBS-D and IBS-C.

Medicines matter too. Rome IV says a subtype can only be confidently established when you are not taking medicines used to treat bowel habit, so a count made while on a laxative or an antidiarrhoeal is provisional. Never stop a prescribed medicine to get a cleaner result without talking to your clinician.

What the calculator cannot do

It does not diagnose IBS. The subtype assumes the IBS criteria are already met, which the Rome IV IBS criteria checker walks through, and a clinician still needs to rule out conditions that look the same, usually with a few blood and stool tests.

Bleeding, weight loss you cannot explain, or symptoms that wake you at night are not part of a subtype. Check them with the gut red flags checker and see a doctor.

Frequently asked questions

How do I know what type of IBS I have?: Count your stools by Bristol type on days when at least one bowel movement was abnormal. More than 25% hard and less than 25% loose is IBS-C, the reverse is IBS-D, more than 25% of both is IBS-M, and anything else is IBS-U.
What is the difference between IBS-C and IBS-D?: Only stool form. IBS-C means hard or lumpy stools (Bristol 1 to 2) make up more than a quarter of bowel movements on abnormal days and loose stools less than a quarter. IBS-D is the exact reverse.
What does IBS-M mean?: IBS with mixed bowel habits. More than 25% of your bowel movements on abnormal days are hard and more than 25% are loose. It is a defined subtype, not a sign that a clinician could not decide.
What is IBS-U?: IBS unclassified. You meet the criteria for IBS, but your stool forms do not reach the thresholds for IBS-C, IBS-D or IBS-M. It often changes once more days are logged.
Do normal bowel movements count when working out my IBS type?: Under Rome IV, only days with at least one abnormal bowel movement count. Days when every stool was normal are left out of the sum entirely, which is the main change from Rome III.
Can laxatives or Imodium change my IBS subtype?: Yes. Rome IV says a subtype can only be confidently established when you are not taking medicines used to treat bowel habit. Tell your clinician what you were taking while you logged, and do not stop a prescribed medicine without asking them.
Can your IBS type change over time?: Yes, and it usually does. In a year-long diary study, more than 75% of women with IBS changed subtype at least once, though only 29% swung between IBS-D and IBS-C.
Is it better to work out my IBS type from memory or a diary?: A diary. In one study, recalled and diary-recorded subtypes agreed in only 54% of people, and only the diary version tracked how fast the gut was actually moving.

Difference Between IBS-D and IBS-C Explained
IBS-D and IBS-C are separated by one rule: what share of your abnormal stools are loose versus hard. Here is how the rule works and why the label keeps moving.
How to Manage IBS-M Without Overcorrecting
IBS-M is the least studied IBS subtype. What the trials actually tested, why the swing happens, and how to treat one end without triggering the other.
Bristol Stool Type 6: What It Actually Means
Type 6 is mushy stool with ragged edges, meaning your colon passed it along before it finished reabsorbing water. What that does and does not tell you.
What to Eat With IBS-C: What the Trials Support
What to eat with IBS-C: kiwifruit and soluble fibre have the best record for stools and comfort. Prunes, prune juice and rye bread can work but often cramp.
Why Is My Poop Different Every Day?
Stool that changes day to day is normal, even in people with no gut condition. What drives the swings, how much is noise, and what counts as a real change.

Sources

Mearin F, Lacy BE, Chang L, Chey WD, Lembo AJ, Simren M, et al. Bowel disorders. Gastroenterology. 2016;150(6):1393-407.e5. doi:10.1053/j.gastro.2016.02.031
Schmulson MJ, Drossman DA. What is new in Rome IV. J Neurogastroenterol Motil. 2017;23(2):151-63. doi:10.5056/jnm16214
Vasant DH, Paine PA, Black CJ, Houghton LA, Everitt HA, Corsetti M, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut. 2021;70(7):1214-40. doi:10.1136/gutjnl-2021-324598
Sharma A, Rao SSC, Kearns K, Orleck KD, Waldman SA. Review article: diagnosis, management and patient perspectives of the spectrum of constipation disorders. Aliment Pharmacol Ther. 2021;53(12):1250-67. doi:10.1111/apt.16369
Lewis SJ, Heaton KW. Stool form scale as a useful guide to intestinal transit time. Scand J Gastroenterol. 1997;32(9):920-4. doi:10.3109/00365529709011203
Drossman DA, Morris CB, Hu Y, Toner BB, Diamant N, Leserman J, et al. A prospective assessment of bowel habit in irritable bowel syndrome in women: defining an alternator. Gastroenterology. 2005;128(3):580-9. doi:10.1053/j.gastro.2004.12.006
Coletta M, Di Palma L, Tomba C, Basilisco G. Discrepancy between recalled and recorded bowel habits in irritable bowel syndrome. Aliment Pharmacol Ther. 2010;32(2):282-8. doi:10.1111/j.1365-2036.2010.04322.x

Cite this tool

Clairop. IBS Type Calculator. www.clairop.com/tools/ibs-type-calculator. Updated October 3, 2026.

Clairop is a general wellness app for people living with a diagnosed digestive condition. It does not replace professional medical care, diagnosis, or treatment. Always follow your healthcare provider's advice.

Clairop logs meals, symptoms and stool in seconds, then looks for the foods your gut reacts to, including reactions that land days later.

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How to use the IBS Type Calculator

The Rome IV rule for IBS subtypes

The Bristol stool types in plain words

Why your subtype can change

What the calculator cannot do

Frequently asked questions

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Sources

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