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Unit Converter

Convert between 100+ units across length, weight, temperature, area, volume, speed, data, time, pressure, and energy.

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0.1

1 mm = 0.1 cm

🔒 All calculations happen in your browser. Nothing is sent anywhere.

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<iframe src="https://optipix.art/embed/unit-converter" width="100%" height="600" style="border:1px solid #e4e4e7;border-radius:8px;" title="Unit Converter by OptiPix" loading="lazy"></iframe>
<p style="font-size:12px">Free tool by <a href="https://optipix.art/unit-converter">OptiPix Unit Converter</a></p>

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About Unit Converter

Last updated: October 2026

OptiPix Unit Converter handles conversions across 10 categories with over 100 units. Convert length (mm to miles), weight (grams to pounds), temperature (Celsius to Fahrenheit to Kelvin), area, volume, speed, digital data (KB to TB, binary and decimal), time, pressure, and energy. Two-way live conversion updates as you type. Each conversion shows the formula used. Quick-swap button to reverse from/to units. All calculations use pure JavaScript arithmetic with no external dependencies or network calls.

How It Works

Each unit stores a conversion factor relative to a base unit in its category (e.g., meters for length). To convert, the tool multiplies the input by the source factor and divides by the target factor. Temperature uses special formulas since it's not a simple ratio.

Use Cases

  • •Convert between metric and imperial measurements
  • •Calculate temperature conversions for cooking or weather
  • •Convert digital storage units for file management
  • •Convert time zones and duration units
  • •Calculate area and volume for construction projects

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What the Unit Converter is good at - and what it isn't

Most conversions are one multiplication: every unit stores a factor relative to the base unit of its category, so converting is multiply by the source factor, divide by the target. Temperature is the exception, because Celsius and Fahrenheit have different zero points as well as different scales, so it needs a real formula rather than a ratio.

The other thing worth checking is which gallon, ton or mile you mean - US and imperial units share names and differ by up to 20%.

What is the best free unit converter online?

OptiPix Unit Converter handles 100+ units across length, weight, temperature, volume, speed, and data storage with instant, offline-capable conversion in your browser. Unlike UnitConverters.net, it keeps working if the connection drops once the page has loaded.

OptiPix Unit Converter vs unitconverters.net vs Google unit converter vs ConvertUnits

FeatureOptiPixunitconverters.netGoogle unit converterConvertUnits
Runs entirely on your deviceYesNoNoNo
CategoriesLength, weight, temp, volume, area, speed, data, moreComprehensiveCommon unitsComprehensive
Precision controlYesFixedFixedFixed
AdsNoneHeavyNoneHeavy
Live conversion as you typeYesYesYesYes

Competitor details reflect publicly listed free-tier features and may change.

Conversion accuracy notes

All conversions route through SI base units with exact legally-defined factors: the international inch is exactly 25.4mm, the pound exactly 453.59237g, and the US gallon exactly 3.785411784L. Routing through a canonical base unit avoids the compounding rounding errors chained pairwise tables accumulate.

Temperature is handled as the affine transformation it is (offset plus scale, since 0°C is 32°F) rather than a simple ratio - the error every naive 'multiply by factor' implementation makes. Data units distinguish decimal (MB, 10^6) from binary (MiB, 2^20) prefixes explicitly, the source of the 'missing' gigabytes on every hard drive.

Results render with significant-figure awareness so 1 inch shows as exactly 2.54cm rather than 2.5400000000000005 - the floating-point artifact you'll see in quickly-built converters.

Frequently Asked Questions

What categories of units are supported?
Length, weight/mass, temperature, area, volume, speed, digital data, time, pressure, and energy - 10 categories with over 100 units total.
How does temperature conversion work?
Temperature uses specific formulas rather than simple multiplication: °F = °C × 9/5 + 32, K = °C + 273.15, etc.
Does it support binary data units?
Yes. Both decimal (KB, MB, GB = powers of 1000) and binary (KiB, MiB, GiB = powers of 1024) data units are supported.
Can I swap the from and to units?
Yes. Click the swap button (↔) to instantly reverse the conversion direction.
Is any data sent to a server?
No. All conversions are pure arithmetic calculated locally in your browser.
Why does my hard drive show less space than advertised?
Manufacturers use decimal gigabytes (10^9 bytes); operating systems historically report binary gibibytes (2^30 bytes). A '1TB' drive is 1,000,000,000,000 bytes = 931 GiB. Nothing is missing - the units differ by 7.4%.
Is a US gallon the same as a UK gallon?
No. The US gallon is 3.785L; the imperial (UK) gallon is 4.546L - 20% larger. The same split affects pints and fluid ounces, which is why UK pints of beer (568ml) beat US pints (473ml).
How do I convert Celsius to Fahrenheit in my head?
Double the Celsius value, subtract 10%, add 32. So 20°C → 40 - 4 + 32 = 68°F, exact. The reverse: subtract 32, halve, add 10%.
How do I convert inches to centimeters?
Multiply inches by 2.54: 10 inches is exactly 25.4cm, since the inch is defined as 2.54 centimeters. OptiPix Unit Converter does this instantly in both directions along with 100+ other units, runs entirely in your browser, and keeps working offline once the page has loaded.
How do I convert kilograms to pounds?
Multiply kilograms by 2.20462: 70kg is about 154.3lbs. For quick mental math, double the kilograms and add 10%. OptiPix Unit Converter gives the precise figure instantly and also handles stones, ounces, and grams, useful for recipes, shipping weights, and fitness tracking across metric and imperial systems.
What is the formula to convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32: 20°C becomes 68°F. Going the other way, subtract 32 and multiply by 5/9. Useful anchors: -40° is identical in both scales, 0°C is 32°F, and 37°C is body temperature at 98.6°F. OptiPix converts temperatures instantly alongside every other unit category.
How many MB are in a GB?
In decimal units used by drive manufacturers, 1GB equals 1,000MB; in binary units used by operating systems, 1GiB equals 1,024MiB. This is why a "500GB" drive shows about 465GB in Windows. OptiPix Unit Converter handles both conventions so storage and bandwidth calculations come out right.
Is there a unit converter that works offline?
Yes. OptiPix Unit Converter performs all calculations in your browser with no server requests, so once the page has loaded it keeps converting with no connection at all. That makes it dependable for travel, fieldwork, and workshops, and it is free with no app install or ads.

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