19G Thinwall Hypotube Guide & Calculator

Screen 19G example clearance, flow, and stiffness; verify final dimensions and performance with your supplier.

19G Hypotube Calculator

Compare example 19G walls by ID, flow proxy, and bending stiffness.

Select a 19G wall profile

Calculations use fixed nominal OD: 0.0420" (1.067 mm), a selected screening value within the ISO 9626:2016 19G OD range. It is not the standard's 1.10 mm designated metric size.

Flow is a theoretical Poiseuille proxy (ID⁴), relative to RW. Bending stiffness is shown as section moment of inertia relative to RW, assuming the same material and a straight, uniform tube.

Calculation ready — Thin Wall (TW)

Illustrative screening geometry. Confirm the actual ID, tolerances, and wall with the selected supplier.

Inner diameter

0.0315"

0.800 mm

Wall thickness

0.00525"

0.133 mm

Relative Flow Rate

185%

Theoretical proxy vs. RW

Bending Stiffness Proxy

82%

vs. RW; same material basis

Result interpretation

At the selected 0.0420" OD, a wall of 0.00525" yields a nominal ID of 0.0315" and a 185% theoretical laminar-flow proxy. The bending-section proxy is 82% of RW. This stiffness comparison assumes the same material and a straight, uniform tube; neither proxy predicts device performance. Confirm the supplier drawing, tolerances, material, and application-specific flow and mechanical tests before selection.

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Key Conclusions & Engineering Facts

1
Theoretical flow comparison: For the example IDs of 0.0270" RW and 0.0315" TW, the ID⁴ Poiseuille proxy is about 185% of the RW baseline (85% higher) when tube length, fluid, and pressure gradient are held equal. It does not predict delivered device flow.
2
ISO 9626 dimensions and example clearance: ISO 9626:2016 lists 19G at a 1.10 mm designated metric size, with OD 1.030–1.100 mm and minimum IDs by wall class. The 0.0343" ETW / XTW ID in this page is an illustrative 0.0420" OD calculation, not an ISO nominal or compliance claim.
3
Mechanical trade-offs need assembly testing: A thinner wall changes section stiffness, but wall thickness alone cannot predict trackability, torque, pushability, kink, or buckling performance. Test the selected material, length, support, cut pattern, joints, and bend radius as an assembly.
4
Material and process selection: ISO 9626 dimensions apply to rigid stainless steel needle tubing. Nitinol and other materials require supplier-specific dimensions and validation; no alloy choice by itself guarantees kink resistance, corrosion performance, or suitability.

Example Geometry Compared with ISO 9626 Minimum IDs

Example Profile	Screening OD	Calculated ID	Example Wall	Flow Proxy vs. RW	ISO 9626 Min. ID	Design Check
Regular Wall (RW)	0.0420" / 1.067 mm	0.0270" / 0.686 mm	0.0075" / 0.191 mm	100% (Baseline)	0.648 mm	Compare required clearance with drawing limits
Thin Wall (TW)	0.0420" / 1.067 mm	0.0315" / 0.800 mm	0.00525" / 0.133 mm	~185%	0.750 mm	Validate stiffness and bend needs
Extra Thin Wall (ETW / XTW)	0.0420" / 1.067 mm	0.0343" / 0.871 mm	0.00385" / 0.098 mm	~260%	0.850 mm	Verify bend and kink
Ultra Thin Wall (UTW)	0.0420" / 1.067 mm	0.0362" / 0.919 mm	0.0029" / 0.074 mm	~323%	0.891 mm	Test handling and support

Scroll horizontally to compare all columns.

Example IDs are calculated as screening OD minus twice the example wall; flow is (ID ÷ 0.0270")⁴. ISO 9626:2016 separately lists gauge 19 at a 1.10 mm designated metric size (OD range 1.030–1.100 mm) and the class minimum IDs shown. These example geometries are not ISO nominal dimensions or a supplier specification.

Application Suitability & Risk Matrix

Questions to Resolve (TW / ETW)

Clearance: Compare the maximum device or guidewire envelope against the minimum tube ID and tolerance stack.
Fluid path: Use the ID⁴ result only for an ideal comparison; set real flow requirements with length, fluid properties, pressure, fittings, and surface condition.
Flexible shafts: Assess material, span, support, cut pattern, joints, and minimum bend radius on the complete assembly.

Do Not Infer from Wall Thickness Alone

Torque or pushability: The section calculation does not predict shaft response or 1:1 torque transfer.
Pressure rating: Gauge and wall dimensions alone do not establish burst or working-pressure limits.
Kink, buckling, and handling: These need application-specific tests; no universal safe bend radius is inferred here.

Methodology & Evidence Sources

This tool is designed for early-stage engineering screening (published 2026-09-26; reviewed 2026-10-06). It combines an illustrative 0.0420" geometry with standard minimum-ID references; calculated values do not certify a product or design.

-
Standards Reference: ISO 9626:2016 applies to rigid stainless steel needle tubing. Its Table 1 lists 19G at a 1.10 mm designated metric size, an OD range of 1.030–1.100 mm, and minimum IDs of 0.648 mm (RW), 0.750 mm (TW), 0.850 mm (ETW), and 0.891 mm (UTW). Confirm the applicable edition and supplier drawing for procurement; ISO dimensions do not define Nitinol or flexible / laser-cut assembly performance. The Extra Thin Wall abbreviation varies by supplier: ISO 9626 and K-Tube use ETW, while New England Small Tube lists XTW. Confirm the supplier's own drawing and terminology.
-
Flow Rate Calculation: The relative flow proxy uses ID⁴ from Poiseuille's relationship for an ideal straight tube. It assumes the same length, fluid, and pressure gradient, and does not model fittings, entrance / exit effects, actual roughness, non-Newtonian behavior, or a device's operating conditions.
-
Stiffness Proxy: Bending-section stiffness is compared using the annulus area moment of inertia, I = π(OD⁴ − ID⁴) / 64. The displayed ratio assumes the same material and a straight, uniform cross-section; it does not predict deflection or performance of slots, joints, supported shafts, or finished devices.

Have a fixed envelope or tolerance stack? Share the drawing so the supplier can review the controlled dimensions.

Submit a 19G drawing for review

Frequently Asked Questions

Does 19G define one exact outer diameter?

No. ISO 9626:2016 lists gauge 19 at the 1.10 mm designated metric size, with an OD range of 1.030–1.100 mm. This screen selects 1.067 mm (0.0420 in) as one comparison point within that range; use the supplier drawing for a released dimension.

How much more theoretical flow does the example TW geometry show?

At the same length, fluid, and pressure gradient, the ideal Poiseuille comparison for the example IDs (0.0315 in TW vs. 0.0270 in RW) is about 185% of baseline, or 85% higher. This is a theoretical ID⁴ proxy, not an expected device flow rate.

When should I consider Extra Thin Wall (ETW / XTW)?

Consider it when the required clearance cannot be met by a thicker wall, then check section stiffness and validate bend, kink, torque, and handling requirements on the complete assembly. ISO 9626 uses ETW for this class; suppliers may use XTW. The example dimensions here are screening inputs, not a purchase specification.

Are 19G thinwall hypotubes available in Nitinol?

Availability and dimensions are supplier-specific. ISO 9626 covers rigid stainless steel needle tubing, so it does not establish Nitinol dimensions or performance. Confirm alloy, material condition, transformation requirements, tolerances, and application testing directly with the supplier.

How do tolerances affect 19G thin wall hypotubes?

Do not assume a universal OD, ID, or wall tolerance. Identify the controlled dimensions, concentricity, material condition, and inspection method on the supplier drawing, then check the worst-case clearance and remaining wall against the design requirements.

Can this calculator predict kink, burst, or device performance?

No. It screens ideal straight, uniform cross-sections only. Actual behavior depends on material, temper, length, cut pattern, joints, support, bend radius, surface condition, pressure, and assembly details. Validate the finished configuration using requirements-specific testing.

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