Millidarcy (mD)
The millidarcy is one thousandth of a darcy and the everyday unit for oil and gas reservoirs: tight gas is below 0.1 mD, good sandstone reservoirs 100–1000 mD.
Symbol: mD
Quantity: intrinsic permeability of a porous medium
SI relation: 1 mD = 9.869233 × 10⁻¹⁶ m²
Derivation: 1 mD = 10⁻³ D = 9.869233 × 10⁻¹⁶ m².
Exact: no, measured or rounded value
Typical uses
- Reservoir rock classification
- Core-flood tests
- Shale and tight-gas permeability
Convert millidarcies to other units
| Conversion | 1 mD equals | Reverse |
|---|---|---|
| millidarcy to square metre | 9.869233 × 10⁻¹⁶ m² | square metre to millidarcy |
| millidarcy to darcy | 0.001 D | darcy to millidarcy |
| millidarcy to square micrometre | 0.0009869233 µm² | square micrometre to millidarcy |
| millidarcy to square centimetre | 9.869233 × 10⁻¹² cm² | square centimetre to millidarcy |
Open the Permeability Converter (Darcy, Millidarcy, m²) to convert any value between all units.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "darcy".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Millidarcy (mD). Retrieved October 29, 2026, from https://scientificconverters.com/units/millidarcy/
IEEE
Scientific Converters, "Millidarcy (mD)," scientificconverters.com. Accessed: Oct. 29, 2026. [Online]. Available: https://scientificconverters.com/units/millidarcy/