Microns (µm) to Millimetres Converter

How it is calculated

A micron (µm) is a millionth of a metre and a millimetre is a thousandth of a metre, so one millimetre holds 1,000 microns. The tool applies mm = µm × 0.001 and m = µm × 0.000001. The millimetre value is rounded to 4 decimals, while the metre value is written in scientific notation with 4 decimals (for example 2.5000e-5 m means 2.5 × 10^-5 m). Because the millimetre output stops at four decimals, very small inputs, below about 0.05 µm, show as 0.0000 mm; use the metre output for those. Zero and negative values are accepted and simply scaled.

Common mistakes

• Shifting the decimal point the wrong way. To go from µm to mm divide by 1,000, so 25 µm is 0.025 mm and not 25,000 mm.
• Confusing microns (µm) with millimetres or with nanometres. 1 µm is 1,000 nm, and 1 mm is 1,000 µm.
• Reading 2.5000e-5 m as 2.5 m. The e-5 means multiply by 10^-5, so it is 0.000025 m.
• Reading 0.0000 mm as zero for a tiny value. The millimetre output is rounded to four decimals; a 0.00004 µm input appears as 0.0000 mm but 4.0000e-11 m.