Convert Nanometers to Millimeters

The Nanometer (symbol: nm) is a unit of surface roughness. A surface-roughness unit equal to exactly 0.001 μm = 10⁻⁹ m. Nanometer-level roughness specification (typically reported as nm Rq RMS, not nm Ra) is required for: precision optical surfaces (mirrors for large-aperture telescopes per ESO E-ELT primary-mirror specification < 1 nm RMS over relevant spatial frequencies; EUV lithography photomask substrates for ASML scanners 0.2-0.5 nm RMS per SEMI P37 / P38 specifications), silicon wafer manufacturing (300 mm prime wafers achieve 0.1-0.3 nm Ra over the polished surface after CMP per SEMI M1 standard), and high-performance hydrodynamic / hydrostatic precision bearings (turbomolecular vacuum pump bearings, atomic-clock-grade reference flats). Atomic-Force Microscopy (AFM — Bruker Dimension Icon, Park Systems NX, Asylum MFP-3D) and white-light interferometry (Zygo, Bruker, Sensofar) resolve surface variations down to sub-nanometer (<0.1 nm RMS) over micrometer-scale fields. The IUPAC 2014 official roughness conversion convention recommends nm only when the underlying measurement instrument resolves <10 nm features — otherwise μm is preferred. Used heavily in EUV photomask qualification, optical-table flat-mirror specs, and semiconductor wafer-flatness GBIR/SFQR metrics.

It belongs to the metric measurement system.

Nanometers are commonly used in machining, quality control, and tribology.

The Millimeter (symbol: mm) is a unit of surface roughness. A roughness unit equal to exactly 1,000 μm — used for very coarse surfaces where μm-Ra would produce unwieldy 4-5 digit numbers: sand-cast metal surfaces before machining cleanup (cast-iron sand-cast Ra typically 0.5-3 mm = 500-3,000 μm), raw cut-off saw and oxyacetylene-cut steel surfaces in steel fabrication, weld-bead surface finish before grinding, and most importantly the absolute roughness ε of pipe inner walls in fluid-mechanics Darcy-Weisbach pipe-flow friction calculations per the Moody diagram / Colebrook-White equation. Standard pipe-roughness reference values per Crane Technical Paper 410 / ASHRAE Handbook Fundamentals chapter 22: drawn copper tubing ε = 0.0015 mm (1.5 μm); commercial steel pipe ε = 0.045 mm; galvanized iron ε = 0.15 mm; cast iron ε = 0.26 mm; concrete pipe ε = 0.3-3.0 mm; riveted steel pipe ε = 0.9-9.0 mm. These mm ε values are used directly in the Colebrook equation 1/√f = -2·log₁₀(ε/(3.7D) + 2.51/(Re·√f)) to compute friction factor f for any pipe Reynolds number Re and diameter D. HVAC duct designers per ASHRAE 90.1 and water-distribution engineers per AWWA M11 standards use mm pipe roughness daily.

It belongs to the metric measurement system.

Millimeters are commonly used in machining, quality control, and tribology.