Convert Square Micrometres to Millidarcies (um2 to mD)

Formula

mD = µm² × 1013.249965828

Derivation from SI units:

• 1 µm² = 10⁻¹² m², almost exactly one darcy (1 D = 0.9869 µm²).
• 1 mD = 10⁻³ D = 9.869233 × 10⁻¹⁶ m².
• 1 µm² = 1 × 10⁻¹² m² ÷ 9.869233 × 10⁻¹⁶ m² per mD = 1013.249965828 mD

One unit is a measured value, so the factor is approximate. Square Micrometre definition: square micrometre; Millidarcy definition: millidarcy.

Worked examples

1. A reading of 0.1 µm² converts to 101.3249966 mD.
   0.1 µm² × 1013.249966 = 101.3249966 mD
2. A value of 2 µm² is 2026.499932 mD.
   2 µm² × 1013.249966 = 2026.499932 mD

Where it's used

Square Micrometres are used for petroleum reservoir data in SI, while millidarcies appear in reservoir rock classification. Both measure intrinsic permeability of a porous medium, so the conversion is a fixed factor.

Square Micrometre to other intrinsic permeability units

Frequently asked questions

Sources

• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4 (derived units) and Table 8 (non-SI units accepted for use with the SI).
• 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: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.