Tube Geometry & Flow Calculator
Diameter conversion, non-overlapping packing, cross-sectional area and area-only relative flow
Version 1.1.2
mm
The editable conversion line refers to whichever diameter basis is selected. Enter a value in any unit; the other units update automatically.
The diagram uses browser CSS millimetre units when space permits; exact physical on-screen size depends on device and browser calibration.
Cross-sectional area (CSA) summary
Relative flow capacity
Area-only model: unobstructed outer-lumen cross-sectional area is calibrated to 1.000. No correction is made for length, viscosity, pressure gradient, entrance effects or hydraulic resistance.
mm
No clinical values are intentionally saved by this control.
Equations
Decimal inches
d_in = d_mm / 25.4Decimal-inch diameter is linked bidirectionally with millimetres, French and gauge for the currently selected diameter basis.
French conversion used by this calculator
Fr = pi * d_mmThis preserves the relation specified for the preceding CriticalCare.info diameter/French/gauge calculator. The displayed French value is editable and converts back to diameter with d_mm = Fr / pi.
Gauge conversion
G = 19.375 - 7.807 * ln(d_mm)ln is the natural logarithm. The displayed gauge value is editable and converts back with d_mm = exp((19.375 - G) / 7.807).
Wall-thickness geometry
OD = ID + 2w; ID = OD - 2ww is radial wall thickness. With wall thickness disabled, ID = OD.
Circular cross-sectional area (CSA)
CSA = pi * d^2 / 4Residual outer-lumen area
CSA_residual = CSA_outer,ID - sum(CSA_inner,OD)Each inner tube occupies its complete outer-diameter footprint inside the outer lumen.
Percentage remaining outer-lumen area
% remaining = 100 * CSA_residual / CSA_outer,IDOuter residual relative flow capacity
Q_outer,relative = CSA_residual / CSA_outer,IDInner-tube relative flow capacity
Q_inner,i,relative = CSA_inner,i,ID / CSA_outer,IDTotal relative flowable area
Q_total,relative = Q_outer,relative + sum(Q_inner,i,relative)This is an area-only comparison, not a Poiseuille or hydraulic-resistance flow prediction.
References
- International Organization for Standardization. ISO 10555-1:2023. Intravascular catheters — Sterile and single-use catheters — Part 1: General requirements. 3rd ed. Geneva: ISO; 2023.
- International Organization for Standardization. ISO 10555-8:2024. Intravascular catheters — Sterile and single-use catheters — Part 8: Catheters for extracorporeal blood treatment. 1st ed. Geneva: ISO; 2024.