How do I convert between units?

Choose a category such as length or weight, enter a value and pick the from-unit. The result appears instantly, and the list below shows the value in every other unit of that category.

How do I convert cm to inches or kg to pounds?

Pick Length or Weight, type the value and choose centimeters or kilograms. One inch is exactly 2.54 cm and one pound is exactly 0.45359237 kg.

Does it matter if I mean US or UK units, like fluid ounces?

Yes — double-check which specific unit variant you need for things like fluid ounces or tons. US and UK definitions differ for several common units, and picking the wrong one gives a subtly wrong answer.

How accurate are the conversions?

Factors use exact definitions wherever they exist, such as 1 inch = 25.4 mm, 1 pound = 0.45359237 kg and 1 mile = 1609.344 m. Output is rounded to ten significant digits for display, which is far finer than everyday tasks need.

Why are there two kinds of gallon and ton?

The US gallon is 3.785411784 liters while the UK gallon is 4.54609 liters, and the short ton is 2000 pounds against 2240 for the long ton. The list names each variant, so choose the one your source document uses.

What is the difference between a kilobyte and a kibibyte here?

A kilobyte is 1000 bytes and a kibibyte is 1024 bytes, and the same split applies at mega, giga and tera level. Storage makers usually quote the first and operating systems often report the second, which is why numbers differ.

How does the Fahrenheit and Celsius conversion work?

Temperature uses formulas rather than a single multiplier because the scales start at different zero points. Celsius to Fahrenheit multiplies by 9/5 and adds 32. Kelvin and Rankine are included too, and negative inputs are accepted.

Can it convert cups to grams?

Yes, in the Cooking tab, for nine common ingredients: flour, granulated, brown and powdered sugar, butter, honey, milk, oil and water. It uses a typical weight per US cup, so the grams are approximate. A cup of flour in particular weighs more if it is scooped from the bag than if it is spooned in and leveled. For baking that needs precision, weigh the ingredient.

Which horsepower does it use?

Both are listed. Mechanical horsepower (33,000 foot-pounds per minute) is 745.6998715822702 W, and metric horsepower (75 kilogram-force meters per second) is 735.49875 W. They differ by about 1.4 percent, so pick the one your source uses.

Can I see several target units at once?

All at once, in a way. After you enter a value, the list below the result shows it in every other unit of the chosen category simultaneously, so you can read several answers without touching the To menu. Only the From unit is excluded from the list.

Is -40 the same in Celsius and Fahrenheit?

Yes. -40 degrees Celsius is exactly -40 degrees Fahrenheit, and it is the only temperature where the two scales agree. Pick Temperature, type -40 and both read the same; Kelvin shows 233.15.

Can I link to a conversion?

Yes. As you change the category, the units or the value, the address bar updates (for example ?c=temperature&from=celsius&to=fahrenheit&v=-40). Copy it to share that exact conversion, or reload the page to come back to it. The pages for popular pairs, such as centimeters to inches, have their own addresses under /tool/unit-converter/.

Is my data sent anywhere?

No. All conversions run in your browser.

Home/Converters & Calculators/Unit Converter/Millimeters to Inches

Millimeters to Inches Converter

Convert length, weight, temperature, and more

Files never storedRuns on your device

From

0.03937007874

1 millimeter equals

meter0.001
kilometer0.000001
centimeter0.1
micrometer1,000
nanometer1,000,000
mile6.213712e-7
yard0.001093613298
foot0.003280839895
inch0.03937007874
nautical mile5.399568e-7

How to convert millimeters to inches

Multiply the millimeter value by 0.03937007874 to get inch, or divide by 25.4. So 1 millimeter = 0.03937007874 inch.

Millimeters to Inches: common values
millimeter	inch
1	0.03937007874
2	0.07874015748
5	0.1968503937
10	0.3937007874
20	0.7874015748
25	0.9842519685
50	1.968503937
100	3.937007874
500	19.68503937
1,000	39.37007874

Reading results never uses a trial use. Copying, saving or printing uses 1 per visit.

About Unit Converter

Converts values between different units of measurement — length, weight, volume, area, temperature, speed, time, data, pressure, energy, power, angle, frequency, fuel economy and approximate cooking measures (cups, tablespoons and teaspoons to grams for common ingredients) — across metric, US and UK systems.

Watch: Unit Converter in Action

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How do I convert between units?: Choose a category such as length or weight, enter a value and pick the from-unit. The result appears instantly, and the list below shows the value in every other unit of that category.
How do I convert cm to inches or kg to pounds?: Pick Length or Weight, type the value and choose centimeters or kilograms. One inch is exactly 2.54 cm and one pound is exactly 0.45359237 kg.
Does it matter if I mean US or UK units, like fluid ounces?: Yes — double-check which specific unit variant you need for things like fluid ounces or tons. US and UK definitions differ for several common units, and picking the wrong one gives a subtly wrong answer.
How accurate are the conversions?: Factors use exact definitions wherever they exist, such as 1 inch = 25.4 mm, 1 pound = 0.45359237 kg and 1 mile = 1609.344 m. Output is rounded to ten significant digits for display, which is far finer than everyday tasks need.
Why are there two kinds of gallon and ton?: The US gallon is 3.785411784 liters while the UK gallon is 4.54609 liters, and the short ton is 2000 pounds against 2240 for the long ton. The list names each variant, so choose the one your source document uses.
What is the difference between a kilobyte and a kibibyte here?: A kilobyte is 1000 bytes and a kibibyte is 1024 bytes, and the same split applies at mega, giga and tera level. Storage makers usually quote the first and operating systems often report the second, which is why numbers differ.
How does the Fahrenheit and Celsius conversion work?: Temperature uses formulas rather than a single multiplier because the scales start at different zero points. Celsius to Fahrenheit multiplies by 9/5 and adds 32. Kelvin and Rankine are included too, and negative inputs are accepted.
Can it convert cups to grams?: Yes, in the Cooking tab, for nine common ingredients: flour, granulated, brown and powdered sugar, butter, honey, milk, oil and water. It uses a typical weight per US cup, so the grams are approximate. A cup of flour in particular weighs more if it is scooped from the bag than if it is spooned in and leveled. For baking that needs precision, weigh the ingredient.
Which horsepower does it use?: Both are listed. Mechanical horsepower (33,000 foot-pounds per minute) is 745.6998715822702 W, and metric horsepower (75 kilogram-force meters per second) is 735.49875 W. They differ by about 1.4 percent, so pick the one your source uses.
Can I see several target units at once?: All at once, in a way. After you enter a value, the list below the result shows it in every other unit of the chosen category simultaneously, so you can read several answers without touching the To menu. Only the From unit is excluded from the list.
Is -40 the same in Celsius and Fahrenheit?: Yes. -40 degrees Celsius is exactly -40 degrees Fahrenheit, and it is the only temperature where the two scales agree. Pick Temperature, type -40 and both read the same; Kelvin shows 233.15.
Can I link to a conversion?: Yes. As you change the category, the units or the value, the address bar updates (for example ?c=temperature&from=celsius&to=fahrenheit&v=-40). Copy it to share that exact conversion, or reload the page to come back to it. The pages for popular pairs, such as centimeters to inches, have their own addresses under /tool/unit-converter/.
Is my data sent anywhere?: No. All conversions run in your browser.

How to use Unit Converter

Start with the row of tabs and pick a category: Length, Weight, Volume, Area, Temperature, Speed, Time, Data, Pressure, Energy, Power, Angle, Frequency, Fuel economy or Cooking (approx.). Type your number into the Value box under From, then open the From menu and choose the unit you have. Open the To menu and choose the unit you want. The answer appears in the highlighted box as you type, with no button to press.

Beneath, a list shows the same value in every other unit of that category, which helps when you are unsure which unit you need. The arrows button between the two menus swaps From and To. Changing the category resets both menus to the first two units of the new tab, so pick your units again after switching. Negative numbers are accepted, which matters for temperature and angles. In the Cooking tab an extra Ingredient menu appears, and the units are US cups, tablespoons and teaspoons, milliliters, grams and ounces by weight.

When to use it

Useful when a recipe lists US cups and your kitchen measures in milliliters, when a spec sheet mixes psi and bar, or when you want to turn miles per gallon into liters per 100 km before comparing cars. It also helps for translating storage sizes between gigabytes and gibibytes, which the tool lists as separate units, for turning horsepower into kilowatts, radians into degrees, or rpm into hertz.

When not to use it

It does not convert currencies, because exchange rates move and the page has no rate source, so use a live currency converter for money. Cooking conversions between cups and grams are only approximate, because they rely on a typical weight per cup for each ingredient and a real cup varies with the brand and with how it is filled. Only nine ingredients are listed, so for anything else weigh it on a kitchen scale.

Tips for best results

Watch the unit names. Gallons, quarts, pints and fluid ounces are listed separately for US and UK, and the ton appears as metric tonne, US short ton and UK long ton. In the Data tab a kilobyte is 1000 bytes while a kibibyte is 1024, which explains why a drive shows less space than its label. Fuel economy runs in opposite directions: more miles per gallon means fewer liters per 100 km. Horsepower comes in two kinds here, mechanical (about 745.7 W) and metric (about 735.5 W). In the Cooking tab, flour is taken as 120 g per US cup; if you scoop it straight from the bag it can weigh noticeably more.

Limitations

Results display up to ten significant digits, with very small or very large values switched to scientific notation, so long decimals are rounded for display. A year is fixed at 365.25 days and no month unit is offered, because months differ in length. In Fuel economy, a value of zero shows a dash, since it has no meaningful reciprocal. Only the listed units are supported. Cooking grams use one typical figure per ingredient and are labelled approximate.

Privacy

Every conversion is plain arithmetic carried out by the page in your browser as you type. The numbers you enter are not saved or transmitted, and there is no field that uploads anything. The one background request is a usage count naming the tool, made after your first interaction, which carries none of the values from your conversions.