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Convert microns (micrometers) to millimeters instantly with our free online calculator. Essential for microscopy, precision manufacturing, semiconductor fabrication, and scientific research.
0.001
Millimeters per Micron
1,000
Microns per Millimeter
10⁻⁶ m
1 Micron in Meters
Formula: Millimeters = Microns × 0.001
| Microns (µm) | Millimeters (mm) | Common Object/Application |
|---|---|---|
| 0.1 µm | 0.0001 mm | Wavelength of ultraviolet light |
| 1 µm | 0.001 mm | Small bacteria, virus particles |
| 5 µm | 0.005 mm | Red blood cell diameter |
| 10 µm | 0.01 mm | Large bacteria, small pollen |
| 25 µm | 0.025 mm | White blood cell, typical pollen |
| 50 µm | 0.05 mm | Fine human hair, thin plastic film |
| 70 µm | 0.07 mm | Average human hair diameter |
| 100 µm | 0.1 mm | Copy paper thickness |
| 250 µm | 0.25 mm | Credit card thickness |
| 500 µm | 0.5 mm | Mechanical pencil lead (0.5mm) |
| 1,000 µm | 1.0 mm | Standard paperclip wire |
| 2,500 µm | 2.5 mm | USB connector thickness |
| 5,000 µm | 5.0 mm | Pencil lead (standard) |
| 10,000 µm | 10.0 mm | Adult fingernail thickness |
| 25,000 µm | 25.0 mm | One inch (approximately) |
A micron (also called a micrometer, symbol: µm) is a unit of length equal to one-millionth of a meter (10⁻⁶ m) or one-thousandth of a millimeter (0.001 mm). The name comes from the Greek word mikros, meaning "small." Microns are the standard unit for measuring microscopic objects and precision dimensions that are too small to measure conveniently in millimeters. The micron sits between the nanometer (1,000 times smaller) and the millimeter (1,000 times larger) on the metric scale, making it perfect for measuring bacteria, cells, fine particles, thin films, and precision-machined parts.
A millimeter (symbol: mm) is a metric unit of length equal to one-thousandth of a meter (10⁻³ m). The word combines the Latin prefix milli (one-thousandth) with meter. Millimeters are widely used for everyday small measurements where centimeters would be too large and microns too small. Common applications include measuring paper thickness, small hardware, jewelry dimensions, rainfall amounts, and precision in carpentry and engineering. A millimeter is visible to the naked eye and is approximately the thickness of a credit card or the width of a standard paperclip wire.
The relationship between these units is exact: 1 micron = 0.001 millimeters, or conversely, 1 millimeter = 1,000 microns. This makes conversion straightforward — simply divide microns by 1,000 to get millimeters, or multiply millimeters by 1,000 to get microns. Understanding this conversion is critical in fields like microscopy, semiconductor manufacturing, precision machining, materials science, filtration technology, and quality control where measurements routinely cross the micron-millimeter boundary.
The formula to convert microns to millimeters is: Millimeters = Microns ÷ 1,000 (or equivalently, Millimeters = Microns × 0.001). Simply divide the number of microns by 1,000 to get the equivalent distance in millimeters.
Question: A human hair measures 70 microns in diameter. What is this in millimeters?
Question: A plastic film is 250 microns thick. Convert to millimeters for a specification sheet.
Note: This is roughly the thickness of a credit card.
Question: A semiconductor chip has features 5 microns wide. What is this in millimeters?
For quick conversions, move the decimal point three places to the left. For example: 2,500 microns becomes 2.500 millimeters (or 2.5 mm). This works because dividing by 1,000 is the same as shifting the decimal. If there is no decimal point, imagine one at the right end of the number. So 750 microns has an implied decimal at 750.0, and moving it three places left gives 0.750 millimeters (or 0.75 mm).
| Specimen | Microns | Millimeters |
|---|---|---|
| Virus particle | 0.1–0.3 µm | 0.0001–0.0003 mm |
| Small bacterium | 1–2 µm | 0.001–0.002 mm |
| Red blood cell | 6–8 µm | 0.006–0.008 mm |
| White blood cell | 10–30 µm | 0.01–0.03 mm |
| Human egg cell | 100 µm | 0.1 mm |
| Pollen grain | 20–100 µm | 0.02–0.1 mm |
| Dust mite | 250–300 µm | 0.25–0.3 mm |
| Material/Component | Microns | Millimeters |
|---|---|---|
| Aluminum foil | 15–20 µm | 0.015–0.02 mm |
| Plastic wrap (cling film) | 10–15 µm | 0.01–0.015 mm |
| Latex glove | 100–200 µm | 0.1–0.2 mm |
| Copy paper | 100 µm | 0.1 mm |
| Human hair | 50–100 µm | 0.05–0.1 mm |
| Plastic bag | 20–50 µm | 0.02–0.05 mm |
| Credit card | 760 µm | 0.76 mm |
| CD/DVD disc | 1,200 µm | 1.2 mm |
| Particle Type | Microns | Millimeters |
|---|---|---|
| Cigarette smoke | 0.1–0.5 µm | 0.0001–0.0005 mm |
| PM2.5 air pollution | 2.5 µm | 0.0025 mm |
| PM10 air pollution | 10 µm | 0.01 mm |
| Fine sand | 100–500 µm | 0.1–0.5 mm |
| Beach sand | 200–2,000 µm | 0.2–2.0 mm |
| Coffee grounds | 500–800 µm | 0.5–0.8 mm |
Modern manufacturing requires tolerances in microns for machined parts, while technical drawings often use millimeters. Engineers must convert between units to specify clearances, surface finishes, coating thicknesses, and dimensional tolerances for quality control.
Biologists measure cells, bacteria, and tissue samples in microns under microscopes, but report findings in scientific papers using both microns and millimeters depending on context. Accurate conversion ensures clarity when comparing cellular structures with larger anatomical features.
Air filters, water purifiers, and industrial filtration systems specify particle removal in microns (e.g., PM2.5 means 2.5 microns). Converting to millimeters helps compare filter specifications with pore sizes and understand filtration effectiveness across different industries.
Chip manufacturing involves features measured in microns (or nanometers for modern chips). Process engineers convert between microns and millimeters when specifying wafer dimensions, layer thicknesses, photolithography resolutions, and inspection standards.
The fastest mental conversion is to shift the decimal three positions to the left. 5000 µm becomes 5.000 mm instantly.
Your millimeter result should always be smaller than your micron input. If 100 microns gives you 100 millimeters, you made an error.
For sub-micron measurements, scientific notation is clearer: 0.5 µm = 5×10⁻⁴ mm is easier to read than 0.0005 mm.
Multiplying microns by 1,000 converts to nanometers, not millimeters. To get millimeters, you must divide by 1,000 or multiply by 0.001.
A micrometer (the tool) measures in microns (the unit). The tool is also called a "mic" or "micrometer caliper" to avoid confusion with the unit.
The conversion is exact: 1 µm = 0.001 mm always. In manufacturing and science, use the full precision — approximations can cause quality failures.
One micron (micrometer) equals exactly 0.001 millimeters. This means you need 1,000 microns to make 1 millimeter. To convert microns to millimeters, divide by 1,000 or multiply by 0.001. For example, 500 microns equals 0.5 millimeters.
Yes, micron and micrometer are two names for the same unit. Both equal one-millionth of a meter (10⁻⁶ m). The symbol µm is used for both. The term micrometer is the official SI unit name, while micron is the more commonly used colloquial term, especially in manufacturing and microscopy.
Divide the number of microns by 1,000 (or multiply by 0.001). For example: 2,500 microns ÷ 1,000 = 2.5 millimeters. For quick mental math, move the decimal point three places to the left. So 750 microns becomes 0.750 millimeters.
100 microns equals 0.1 millimeters. This is roughly the thickness of standard copy paper, a thin plastic bag, or a human hair (which typically ranges from 50-100 microns). To calculate: 100 ÷ 1,000 = 0.1 mm.
A human hair typically ranges from 50 to 100 microns in diameter, with an average of about 70 microns. This equals 0.05 to 0.1 millimeters. Hair thickness varies based on genetics, ethnicity, age, and whether the hair is fine, medium, or coarse.
Microns provide whole numbers for very small measurements, making them easier to read, communicate, and work with than decimal millimeters. For example, 25 microns is clearer than 0.025 millimeters in manufacturing specifications. This reduces measurement errors and simplifies quality control in precision industries.
Microns are widely used in microscopy (cell and bacteria sizes), precision manufacturing (machining tolerances), air filtration (particle sizes), plastics industry (film thickness), textiles (fiber diameter), semiconductor manufacturing (chip features), medical devices, and paint coating thickness. Any field requiring precision measurement of objects between 1-1000 micrometers typically uses microns.
One micron is extremely small: about 1/25,000th of an inch, or 1/1,000th of a millimeter. You cannot see individual microns with the naked eye. For reference: bacteria are 1-10 microns, red blood cells are 7-8 microns, white blood cells are 10-30 microns, pollen grains are 10-100 microns, and fine sand particles are 100-500 microns.
This calculator uses the internationally recognized conversion factor of 1 micron = 0.001 millimeters. For scientific research, precision manufacturing, and quality control applications requiring extreme accuracy, always verify measurements with calibrated instruments and refer to applicable industry standards (ISO, ASTM, etc.).