Medical Oncologist
CION Cancer Clinics
Measuring and cutting the stoma baseplate | CION Cancer Clinics
Cut the hole in the baseplate just a little bigger than your stoma, leaving a thin, even ring of skin showing, roughly the thickness of a coin. Too tight and it can cut the stoma; too loose and output burns the skin. A new stoma shrinks over the first weeks, so you will re-measure often. Here is how to measure, cut and check the fit. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
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Medically reviewed by Dr. Muralidhar MuddusettyConsultant Surgical Oncologist · MBBS (AIIMS), MS (Surgery, AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh) · last reviewed September 2026, next review due September 2027
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On this page
- How big should the hole in the baseplate be?
- How do I measure and cut it at home?
- Do I have to cut every baseplate myself?
- How can I tell the hole is the wrong size?
- What do families often get wrong about cutting the baseplate?
- When does measuring at home stop being enough?
- Common questions about sizing a stoma baseplate
The short answer
How big should the hole in the baseplate be?
Cut the hole so it sits just a little bigger than the stoma, with a thin ring of skin showing all the way round. The usual guide is a gap of about three millimetres, roughly the thickness of a coin, between the edge of the stoma and the edge of the hole.
Why a small gap matters
The baseplate is the sticky part that holds the bag to your tummy. If the hole is too tight, it rubs the stoma every time you move and can cut it. If the hole is too loose, output sits on the bare skin. Stool and urine are harsh on skin, and within a day or two that ring turns red, wet and sore. Almost every sore-skin problem starts with a hole that no longer fits.
Why you cannot measure once and forget it
A new stoma is swollen after the operation. It slowly shrinks over the first six to eight weeks, and the size you cut in hospital will be too big by the time you are home and eating normally. Weight gain, weight loss and a bulge around the stoma can all change its size later on, too.
The stoma has no nerve endings, so you will not feel it being rubbed or nicked. That is why you check by looking, not by waiting for pain.Step by step
How do I measure and cut it at home?
Use the measuring card
Most boxes of bags come with a printed card of circles. With the old bag off and the skin clean, hold the card over the stoma. Pick the smallest circle that clears the stoma without touching it.
Make a paper pattern
If your stoma is oval or uneven, a circle will not fit. Trace its shape onto the clear film or a piece of paper, add the small gap all round, and cut that out. Keep the pattern in your supply box.
Mark the back of the baseplate
Lay the pattern on the paper backing and draw round it with a pen. Most baseplates have guide rings printed on the back to help you stay centred.
Cut with curved scissors
Small curved scissors give a smooth edge. Run a finger round the cut afterwards. Any sharp point or jagged edge can nick the stoma, so trim it smooth before you peel the backing off.
Check it on the body
After fitting, look at the ring of skin showing. It should be thin and even. If you see a wide gap on one side, re-cut the next one rather than living with it.
Not sure whether this applies to you?
Ask an oncologistWhat is in the box
Do I have to cut every baseplate myself?
Not always. There are three kinds, and your stoma nurse will suggest one based on the size and shape of your stoma.
Cut-to-fit
The baseplate comes with a small starter hole, and you cut it to size. This is what most people use in the early weeks, because the stoma is still changing shape.
Suits
- A new stoma that is still shrinking
- An oval or uneven stoma
Pre-cut
The hole is already cut to a set size. It saves time and helps people with poor eyesight or stiff hands. It only works once the stoma has settled and is round.
Order a size only after your stoma nurse confirms the size has been steady for a while.Mouldable
You roll the soft edge of the hole back with your thumbs until it hugs the stoma. No scissors are needed. It can suit a stoma that changes size through the day, though it is not stocked by every shop.
Reading the signs
How can I tell the hole is the wrong size?
Hole too small
Hole too big
A pale or white line on the stoma where the edge presses
A red, raw ring of skin close to the stoma
Small spots of blood on the baseplate edge
Output found under the baseplate when you peel it off
The stoma looks squeezed or pushed out of shape
Itching or burning around the stoma between changes
The baseplate lifts because it will not sit flat
Leaks that keep coming back on the same side
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When to call the same day
A healthy stoma is pink or red and moist. If it turns dark purple, grey or black, or you cut into it and the bleeding does not settle with gentle pressure, call your surgical team or go to the emergency department the same day. Do not wait for the next routine change to see whether it improves.
Commonly believed
What do families often get wrong about cutting the baseplate?
"Cut it a bit bigger, just to be safe."
A generous hole feels kinder to the stoma, but it leaves skin open to output. The skin under a loose baseplate breaks down quickly, and sore skin makes the next bag stick even worse. A small, even gap is the safer choice.
"The size they gave us in hospital is the size for life."
The stoma is at its biggest in the days after surgery. As the swelling goes down, the hole needs to come down with it. Measure at every change in the early weeks, then every few weeks once the size has settled.
"If it does not hurt, the fit must be fine."
The stoma itself cannot feel pain, so a tight edge can injure it without any warning. The skin around it can feel, but by the time it stings it is already damaged. Look at the stoma and skin at every change.
"Kitchen scissors will do."
Straight blades leave corners and rough edges. Keep a small pair of curved scissors only for baseplates, clean and dry, in the same box as your bags.
Being straight with you
When does measuring at home stop being enough?
This page gives the general method. It cannot see your stoma. Some stomas need a fit that a card and scissors will not solve, and a stoma nurse should look at those.
Stomas that often need extra help
A stoma that sits flat with the skin, or dips below it, may need a curved baseplate, called convex, that presses gently to make it stand out. A stoma close to a skin fold, the belly button or a scar can leak whatever the hole size. A bulge around the stoma changes its shape when you stand and sit. In each case, cutting the hole more carefully will not fix the leak.
If someone else does the cutting
Many older patients rely on a son, daughter or spouse to cut and fit the bag. Ask the stoma nurse to watch that person do one full change before you leave hospital. Write the size on the box, and keep a spare pattern in case the usual helper is away.
Bring a used baseplate, peeled off and in a bag, to your stoma clinic. The pattern of staining on the back shows the nurse where it is leaking.Questions we are asked
Common questions about sizing a stoma baseplate
How often should I measure my stoma?
At every bag change for the first couple of months, because the stoma is shrinking as the swelling settles. Once the size has stayed the same for a few weeks, checking every few weeks is usually enough. Measure again if you gain or lose weight, or if leaks start that were not happening before.
My stoma is oval. How do I cut for that?
Make your own pattern. Trace the outline onto the clear film or paper, add a small, even gap all round, and cut it out. Use that pattern each time and mark which way is up. Many stomas are not perfectly round, so this is common and not a sign that anything is wrong.
Can I cut a stack of baseplates in advance?
Yes, once your size has settled. Cutting a week's worth at a time saves effort, especially if a family member does it. In the early weeks after surgery, cut one at a time, because the size you need may change between one change and the next.
My stoma is bigger at some times of day. What should I do?
A stoma can swell slightly after meals or when active. Size the hole for the larger measurement so it never pinches. If the gap then causes sore skin at other times, ask your stoma nurse about a mouldable baseplate or a thin seal ring that fills the gap.
Is a little bleeding from the stoma normal when cleaning?
A small spot of blood when you wipe the stoma is common. The surface has many tiny blood vessels. It should stop within a few minutes with gentle pressure. Bleeding that keeps going, comes from inside the stoma, or keeps coming back where the edge touches needs a call to your team.
Do I need a seal ring as well as the right hole size?
Not everyone does. A soft ring that sits around the stoma can help fill small dips in the skin or an uneven shape. It is an extra cost, so try getting the hole size right first. Your stoma nurse can tell you whether your skin shape needs one.
The measuring card does not have my size. What now?
Use the nearest circle that is larger than your stoma, or make a paper pattern instead. Cards differ between brands, so a card from one company may not match another's baseplate markings. If your stoma is very large or very small, ask about baseplates made for that size.
Who can check my fit if I live outside Hyderabad?
Ask the hospital where you had surgery for the stoma nurse's contact before you go home. Many nurses will look at a clear photo of the stoma and the used baseplate sent by message. If the problem keeps coming back, plan a visit so someone can see it in person.
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Dr. C. Raghavendra Reddy
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MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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Dr. Owais Mohammed
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Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Surgical Oncologist
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Dr. Vinay Mamidala
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Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
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Sources
- American Cancer Society — Colostomy Guide
- American Cancer Society — Ostomies
- NHS — Colostomy
- NHS — Ileostomy
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
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Your First Bag Change After SurgeryThe full change, step by step, before you cut your ownSkin Problems Around a StomaWhat to do when the ring of skin is already soreLeakage: Causes and FixesWhen the hole size is right and it still leaksOne-Piece vs Two-Piece AppliancesHow the bag type changes what you cut
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