Debunking the Myth: How many ml is a normal PEG? Understanding Tube Sizing vs. Volume

November 1, 2025 •

4 min read

While many people ask, 'how many ml is a normal PEG?', this question is based on a common misunderstanding, as PEG tubes are measured by diameter using the French scale, not by volume. For example, the typical range of adult PEG tube sizes is 12 Fr to 24 Fr, while milliliters are used to measure the fluid administered through the tube, not the tube itself.

Quick Summary

This article clarifies the difference between a PEG tube's size (measured in French units) and the volume of liquid (in ml) used for flushing or feeding. It details what a PEG tube is, how different tube sizes are selected, and the key principles of nutrition diet management and care for patients using these devices.

Key Points

Sizing vs. Volume: PEG tubes are measured in French units (Fr) for diameter, not milliliters (ml).
Adult Tube Sizes: Common adult PEG tube sizes range from 12 Fr to 24 Fr, depending on patient factors and formula viscosity.
Flushing is in ml: Milliliters are used for flushing the tube with water (typically 20-30 ml) to prevent clogs.
Feeding Methods: Nutrition can be delivered via bolus feeding (in measured amounts) or continuous feeding (via a pump).
Dietitian's Role: A dietitian determines the specific formula and feeding plan to meet the patient's unique nutritional needs.
Care is Crucial: Routine care, including flushing and site cleaning, is essential to prevent complications like blockages and infection.

Understanding the PEG Tube: Diameter vs. Volume

A Percutaneous Endoscopic Gastrostomy, or PEG, is a medical procedure to place a feeding tube directly into the stomach through the abdominal wall. This method of enteral nutrition is vital for individuals who cannot meet their nutritional needs orally over a prolonged period due to conditions like swallowing difficulties, neurological disorders, or certain cancers. A crucial point of clarification is that the size of a PEG tube refers to its outer diameter, measured in units called "French" (Fr), while milliliters (ml) are the units for liquid volume, such as the formula and water that passes through the tube.

What are French Units (Fr)?

The French scale is a universal gauge used for sizing medical catheters and tubes. One French unit corresponds to one-third of a millimeter in diameter. Therefore, a larger French number indicates a wider tube diameter. This size is a critical factor for healthcare professionals when selecting the appropriate tube for a patient, taking into account factors like the patient's BMI and the viscosity of the feeding formula.

Factors Influencing PEG Tube Size Selection

Choosing the correct PEG tube size is a clinical decision based on several patient-specific factors. A dietitian and a medical team work together to determine the best fit for an individual's nutritional requirements and physical anatomy.

Patient Anatomy and Condition: The patient's age and size are key considerations. Pediatric tubes range from 12 Fr and smaller, while adult tubes are generally larger. For instance, a thin adult might use a 14-16 Fr tube, while a standard feeding may require an 18-20 Fr tube.
Formula Viscosity: Thicker or high-viscosity formulas, or frequent medication administration, may necessitate a wider-bore tube (e.g., 22-24 Fr) to prevent blockages.
Intended Duration: While standard PEG tubes are used for long-term feeding (more than 30 days), the patient's projected needs play a role in the choice of tube type and size.

Delivering Nutrition and Fluids via a PEG Tube

Once the PEG tube is in place, the focus shifts to administering a carefully planned nutrition diet. A dietitian will prescribe a specific formula and a feeding schedule based on the patient's caloric and nutrient needs. There are two primary methods for delivering nutrients:

Bolus Feeding: This involves giving a measured amount of feed and water over a short period, several times a day. It mimics a natural eating pattern and may be administered via a syringe or gravity.
Continuous Feeding: This method uses a pump to deliver a steady, controlled rate of formula over a longer period, such as 24 hours. This is often preferred for those with jejunal tubes or patients who experience feeding intolerance with bolus feeds.

The Role of Milliliters in PEG Tube Care

While the tube size is measured in French units, milliliters are the standard measure for flushing and administering medications or water. Flushing is a crucial part of routine tube care to prevent blockages. For adults, flushing the tube with 20 to 30 ml of water is a standard practice. This is done before and after each feeding or medication administration, and at regular intervals if the tube is not in use.

Bolus vs. Continuous Feeding Comparison

Choosing the right feeding method is a clinical decision based on patient-specific factors like tolerance and nutritional goals. Here is a comparison of the two main strategies:


Aspect	Bolus Feeding	Continuous Feeding
Delivery Method	Measured amounts administered several times per day.	Slow, continuous drip over several hours using a pump.
Timing	Administered over 15-60 minutes, typically 3-6 times daily.	Delivered continuously, often over 12-24 hours.
Physiology	More closely mimics a natural eating schedule.	Constant, steady intake that may be easier for some to tolerate.
Gastrointestinal Tolerance	May cause bloating or fullness; some may experience intolerance.	Often better tolerated by patients who experience bloating or reflux.
Aspiration Risk	No higher risk than continuous feeding, according to recent meta-analysis.	No higher risk than bolus feeding, according to recent meta-analysis.
Mobility	Offers greater freedom and mobility between feedings.	Restricts mobility as the pump is continuously attached.
When Used	Patients with gastric access, stable digestive function.	Patients with jejunal access (PEG-J), or those with feeding intolerance.

Conclusion: The Critical Distinction

In summary, the question of how many ml is a normal PEG is based on a fundamental misconception. PEG tubes are not measured in milliliters but rather by their outer diameter using the French scale. Milliliters, on the other hand, are the unit of measure for the liquid nutrition, medication, and water that pass through the tube. Proper PEG management involves understanding this key distinction, selecting the appropriate French size for the patient, and diligently following the prescribed feeding regimen and flushing protocols, measured in milliliters, to ensure optimal nutrition and minimize complications.

For more detailed information on enteral feeding guidelines, consult reputable medical resources, such as the guidelines provided by the National Institutes of Health (NIH).

Frequently Asked Questions

The French size (Fr) of a PEG tube refers to its outer diameter. A higher French number indicates a larger, wider tube.

PEG tubes are measured by the French scale, where each unit is equivalent to one-third of a millimeter. For example, a 15 Fr tube has a diameter of 5 mm.

Adult PEG tube sizes typically range from 12 Fr to 24 Fr, but the specific size depends on the patient's body mass index (BMI), the viscosity of the feeding formula, and other clinical factors.

For adults, a typical flush involves 20 to 30 ml of water. This is done before and after each feeding or medication administration to prevent the tube from clogging.

Bolus feeding delivers a measured amount of formula several times daily, mimicking meal times. Continuous feeding uses a pump to deliver a steady, controlled rate of formula over a longer period.

Yes, a PEG tube can become clogged, especially if it is not flushed regularly. To prevent clogs, medications should be crushed finely, dissolved in water, and the tube should be flushed before and after use.

While generally safe, complications can include accidental tube dislodgement, infection at the site, tube blockage, and gastrointestinal issues like diarrhea or bloating.