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Permeability

in²tomm²

Convert square inches (permeability) (in²) to square millimetres (permeability) (mm²).

Factor1 in² = 645.16 mm²

Converter

in²

Accepts numbers or expressions, e.g. 150 + 14.7

Result
645.16mm²

Rendered to 6 significant figures.

Formula

Formula
mm² = in² × 645.16

Multiply any value in square inches (permeability) by 645.16 to obtain the value in square millimetres (permeability).

Worked example

Convert 1 in² to mm².

  1. 01Start with 1 in².
  2. 02Multiply by the conversion factor: 1 × 645.16 = 645.16 mm².
Result1 in² = 645.16 mm²

Conversion table

in²mm²
1645.16
21290.3
53225.8
106451.6
2012903
5032258
10064516
2001.2903e+5
5003.2258e+5
10006.4516e+5

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from in² to mm²?
1 in² equals 645.16 mm². To convert, multiply the value in square inches (permeability) by 645.16.
How do I convert 1 in² to mm²?
1 in² = 645.16 mm². For any value, multiply by 645.16.
How do I convert mm² back to in²?
Divide by the same factor — or equivalently, multiply by 0.001550003. So 1 mm² = 0.00155 in².
When would I need to convert square inch (permeability) to square millimetre (permeability)?
Permeability conversions between in² and mm² appear in petroleum and reservoir engineering, hydrogeology, geotechnical engineering, packed-bed filtration and porous-materials research. The darcy (D) and its sub-multiples (mD, µD, nD) dominate petroleum-engineering documentation; SI area-equivalent units (m², µm², mm², cm², ft²) appear in geophysics and porous-media research. Intrinsic permeability is a property of the porous medium alone — this category does NOT include hydraulic conductivity (m/s, requires fluid density and viscosity), gas permeability (Klinkenberg slip corrections) or membrane-permeability coefficients, all of which are different physical quantities and require explicit assumptions.
Is the conversion exact?
The factor shown is precise to at least 7 significant figures. For most process-engineering work this is far better than instrument accuracy. For metrology or trade applications, refer to the relevant national standard (NIST, BIPM, ISO 80000).

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