Peristaltic Pump Tubing Size Guide: ID, OD, Wall Thickness & Tube Numbers

A peristaltic-pump tube cannot be selected from inner diameter alone.

The pump works by squeezing the tube against the pump-head housing. That means three dimensions matter at the same time:

inner diameter (ID), outer diameter (OD), and wall thickness.

ID mainly determines the fluid passage and strongly affects displacement per revolution. Wall thickness determines how the tube is occluded by the rollers. OD follows from those two dimensions and affects how the tube fits guides, retainers and the pump head.

The practical rule is:

Match the pump head first, then match ID + wall thickness, then confirm material and process compatibility.

A tube that has the right bore but the wrong wall can produce poor suction, incomplete occlusion, excessive roller load, rapid wear or no pumping at all.

Decision Summary

Do not treat tube numbers such as #16, #25 or #24 as universal hose sizes. Use the pump manufacturer’s tubing family as the reference, then confirm the actual ID, OD and wall thickness. When changing supplier, buy against dimensions and tolerances—not the tube number printed in a marketplace title.

The Three Dimensions You Need

Inner diameter — ID

ID is the bore through which the fluid moves.

Within the same pump-head family and operating speed, a larger ID generally produces more displacement per revolution and therefore a higher possible flow rate.

But ID alone does not establish compatibility.

Two tubes can have the same 6.4 mm ID and very different wall thicknesses. They may require different pump heads or different occlusion geometry.

Wall thickness — WT

Wall thickness is the elastomer between the fluid bore and the outside surface.

For a round tube:

Wall thickness = (OD − ID) ÷ 2

This dimension is critical because the roller must compress approximately the complete fluid passage without excessively crushing the tube.

Grayline’s peristaltic-tubing guidance notes that even small wall-thickness differences can materially change pump behavior. A wall that is too thin may fail to seal fully; a wall that is too thick can increase compression and wear.

Outer diameter — OD

OD is useful for checking physical fit, but it should not be specified without ID and wall thickness.

For example:

• 3.2 mm ID + 1.6 mm wall → 6.4 mm OD
• 6.4 mm ID + 1.6 mm wall → 9.6 mm OD
• 6.4 mm ID + 2.5 mm wall → 11.4 mm OD

The second and third examples share the same bore but are not the same pump tube.

Common Precision-Tubing Numbers

The following table uses one common numbered-size convention published by Runze for silicone peristaltic tubing. It closely resembles widely used L/S-style sizing, but it should be treated as a manufacturer-specific reference, not an international tube-number standard.

Tube No.	ID	OD	Wall Thickness
#13	0.8 mm	4.0 mm	1.6 mm
#14	1.6 mm	4.8 mm	1.6 mm
#19	2.4 mm	5.6 mm	1.6 mm
#16	3.2 mm	6.4 mm	1.6 mm
#25	4.8 mm	8.0 mm	1.6 mm
#17	6.4 mm	9.6 mm	1.6 mm
#18	7.9 mm	11.1 mm	1.6 mm

The useful pattern is clear: these sizes share a nominal 1.6 mm wall while the bore increases.

That lets a compatible pump-head family cover a useful flow range without changing the basic compression concept.

Masterflex publishes comparable L/S Precision sizes. Its current technical material lists L/S 13 at about 0.8 mm ID, L/S 14 at 1.6 mm, L/S 16 at roughly 3.1–3.2 mm, L/S 25 at 4.8 mm, L/S 17 at 6.4 mm and L/S 18 at approximately 7.9 mm.

Those similarities are useful for cross-checking, but they do not mean every supplier’s “#16” is automatically interchangeable with genuine L/S 16 tubing.

High-Performance Tube Numbers Use a Thicker Wall

Another common family includes #15, #24, #35 and #36.

Runze lists this group with a nominal wall around 2.5 mm:

Tube No.	ID	OD	Wall Thickness
#15	4.8 mm	9.8 mm	2.5 mm
#24	6.4 mm	11.4 mm	2.5 mm
#35	7.9 mm	12.9 mm	2.5 mm
#36	9.6 mm	14.6 mm	2.5 mm

Masterflex’s high-performance L/S family uses the same general concept: thicker-wall tubing intended for applications where pressure, suction lift, viscous fluids or longer service life matter.

The important buying lesson is not the exact wall value from one supplier.

It is the distinction between:

standard precision wall and high-performance thicker wall

A buyer who orders #24 because its 6.4 mm ID matches a previous #17 tube can still receive a tube that is mechanically incompatible with the installed head.

Tube Number Is Not a Universal Standard

This is one of the most important points in replacement sourcing.

Numbers such as:

13 / 14 / 16 / 25 / 17 / 18 / 15 / 24 / 35 / 36

are widely recognized in the peristaltic-pump market, but the number itself should not be your only specification.

Different suppliers may:

• imitate a common size family;
• round metric dimensions differently;
• use a different wall tolerance;
• sell a similar tube number in a different material hardness;
• use the number as a compatibility shorthand rather than a dimensional standard.

There is no reason to assume a generic marketplace “#25” has the same dimensional tolerance and mechanical behavior as the pump manufacturer’s approved #25 tubing.

When replacing OEM tubing, record the real dimensions and the original part number.

Why Wall Thickness Controls Occlusion

Occlusion is the degree to which the rollers compress the tube.

If the tube is under-compressed, the fluid passage may not close completely. Possible symptoms include:

• loss of suction lift;
• backflow;
• poor repeatability;
• lower-than-expected flow;
• inability to prime.

If the tube is over-compressed, the pump may show:

• excessive tubing wear;
• higher roller load;
• increased drive torque;
• heat generation;
• shortened tube life.

The correct wall therefore depends on pump-head geometry, not on flow requirement alone.

This is why a size chart should be used to identify candidates, while the pump-head manual determines final compatibility.

How to Measure Existing Tubing

If the original part number is missing, measurements can help reconstruct the specification.

Use an unworn section outside the roller track.

Do not measure the visibly flattened section inside the pump head and assume that is the original OD.

Record:

ID:
OD:
Calculated wall:
Material, if known:
Color:
Hardness, if known:
Pump model:
Pump-head model:

ASTM D3767 provides general practice for dimensional measurement of rubber products and notes that measuring pressure can affect readings on soft flexible materials. That matters here: squeezing silicone tubing with a caliper can produce a falsely small OD or wall estimate.

For a sourcing specification, use controlled measurement and ask the supplier for dimensional tolerance.

Size Also Changes Flow

Within a compatible tubing family, increasing ID increases the volume displaced as the roller advances.

Masterflex’s published L/S data illustrates the magnitude of that effect: its precision tubing family progresses from very small flow capability at L/S 13 to much larger flow ranges at L/S 17 and L/S 18.

Those published flow ranges are manufacturer- and pump-dependent. They should not be copied as universal flow ratings for generic tubing.

Actual flow depends on:

• pump-head geometry;
• number of rollers;
• RPM;
• tube ID;
• tube recovery;
• material hardness;
• pressure;
• fluid viscosity;
• tubing age.

For metering applications, recalibrate after changing the tube—even if the nominal tube number stays the same.

Do Not Ignore Hardness

Two tubes with identical ID, OD and wall thickness can still behave differently if their elastomer hardness and recovery characteristics differ.

ASTM D2240 defines standardized durometer methods for elastomer hardness. In commercial pump-tubing specifications, Shore A is commonly used.

A softer tube may occlude easily but deform differently under load. A harder tube may require more force and may not behave correctly in a head designed for another formulation.

Therefore, a serious replacement specification should contain:

dimensions + material + hardness/formulation + pump-head compatibility

not just dimensions.

Size Selection Workflow

Use this sequence when replacing tubing.

1. Identify the pump head

Record the manufacturer, pump model and head model.

2. Find the approved tubing family

Check the original manual or manufacturer tubing chart.

3. Record the original part number

This is the cleanest cross-reference when changing supplier.

4. Confirm ID, OD and wall thickness

Do not rely on the tube number alone.

5. Decide whether you need standard or thicker-wall tubing

Do not change wall family merely to gain flow.

6. Confirm material and hardness

Mechanical fit and chemical compatibility must both pass.

7. Order a sample length if changing supplier

Fit-test and recalibrate before buying bulk.

8. Freeze the approved replacement specification

Record the supplier SKU, dimensions, material, tolerance and lot/document requirements so the next replacement is repeatable.

Current Alibaba Options for Different Buying Roles

The current marketplace contains hundreds of peristaltic-tubing offers. For this article, the useful offers are not three identical silicone listings; they represent different procurement situations.

Low-MOQ replacement — Kamoer silicone tubing

Kamoer’s current Alibaba listing is clearly positioned as peristaltic-pump silicone tubing and currently shows a 1 meter MOQ, making it useful for a buyer who wants to confirm fit before ordering a larger quantity.

Use this role for sample replacement and fit verification, not as evidence that every Kamoer size fits every pump head.

Numbered-size bulk replacement — Ruixiang silicone tubing

Ruixiang’s current listing explicitly advertises multiple common tube numbers including #13, #14, #15, #16, #17, #18, #19, #24 and #25. Current Alibaba search data shows a 50 meter MOQ and an established sales history.

This role is better suited to repeat replacement or bulk procurement after the required dimensions have already been validated.

Alternative-material replacement — JIHPUMP Norprene A-60-G

For applications where silicone is not the intended material, JIHPUMP currently lists Norprene A-60-G peristaltic-pump tubing with a 1 meter MOQ.

This is an alternative-material sourcing route, not a drop-in recommendation. Confirm exact dimensions, wall construction, chemical compatibility and pump-head approval before changing material.

Buyer Check: Marketplace size names, prices, MOQ and available variants can change. Confirm the exact ID, OD, wall thickness, material grade and current supplier specification before placing an order.

What to Put on the Purchase Order

A repeatable tubing PO should specify more than “silicone #16.”

Use:

Pump / pump-head model
Original tube part number
Tube-number reference
ID
OD
Wall thickness
Dimensional tolerance
Material / formulation
Hardness if specified
Required length
Quantity
Operating fluid
Operating temperature
Pressure / suction condition
Required documentation

If the supplier cannot confirm the three basic dimensions, do not treat the tube number as sufficient evidence of compatibility.

Frequently Asked Questions

Is #16 tubing always 3.2 mm ID?

It is commonly around 3.1–3.2 mm in widely used L/S-style families, but the tube number is not an international dimensional standard. Confirm the supplier’s actual dimensions.

Can I replace #17 with #24 because both are around 6.4 mm ID?

Not automatically. They can use different wall thicknesses and may require different pump-head geometry.

Does larger ID always mean more flow?

Within a compatible pump family, larger ID generally increases displacement, but actual flow also depends on pump speed, head geometry, material, pressure and tubing condition.

Can I measure a worn tube to identify its size?

Use an unworn section. The portion under the rollers can be permanently flattened and may no longer represent the original OD or wall.

Why does new tubing change my calibrated flow?

Dimensional tolerance, stiffness, occlusion and elastic recovery can differ from the worn tube. Recalibrate dosing systems after replacement.

Final Takeaway

Peristaltic-pump tubing size is a mechanical compatibility specification, not just a bore diameter.

Use ID, OD and wall thickness together.

Tube numbers are useful shorthand, but they do not remove the need to confirm the pump-head family and actual dimensions. A 6.4 mm-ID standard-wall tube and a 6.4 mm-ID thick-wall tube can be completely different replacements even though both carry fluid through the same bore.

The correct workflow is:

pump head → approved tubing family → tube number → ID/OD/wall → material/hardness → sample fit → flow recalibration → repeat-purchase specification

Once those fields are standardized, replacement tubing becomes a repeatable procurement item rather than a trial-and-error hose purchase.