Convert length, weight, temperature, area, volume, speed, and data units instantly. cm to inches, kg to lbs, °C to °F and 60+ more — free and offline-capable.
7 Measurement Categories 60+ Units Supported Exact Legal Conversion Factors Works Fully Offline
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Unit Converter is a free, browser-based tool
from UseToolSuite's
Productivity Tools collection.
All processing happens locally on your device — your data is never uploaded to any server.
Use the tool below, then scroll down for detailed documentation, frequently asked questions, and related resources.
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Common conversions
One Converter for Every Everyday Measurement
The Unit Converter handles the conversions that come up constantly in real life and work: centimeters to inches for furniture and screens, kilograms to pounds for shipping and fitness, Celsius to Fahrenheit for recipes and travel, square meters to square feet for property listings, liters to gallons for fuel, and megabytes to gigabytes for storage. Everything computes instantly in your browser with the exact legal conversion factors — no ads-riddled result pages, no "premium" precision tiers.
Exact Factors, Not Approximations
Conversions between metric and imperial units are not measured — they are defined. One inch is exactly 25.4 mm, one pound exactly 0.45359237 kg, one US gallon exactly 3.785411784 liters. This converter carries those definitions at full precision through a single base-unit step, so chained conversions (miles → km → m → feet) never accumulate rounding drift the way calculators using shortened factors do.
Works Offline, Forever Free
Conversion factors are constants, so nothing here needs a server: the tool works on a plane, in a basement, or behind a corporate firewall. There is no lookup quota, no email wall, and no watermarked output — a table of multiplication factors is not something anyone should charge for.
The two mistakes behind almost every conversion error
The first is rounding too early. Converting 26 miles through “1 mile ≈ 1.6 km” gives 41.6 km; the exact factor 1.609344 gives 41.84 km — a 240-meter error that would misplace a marathon finish line. The rule: convert with full precision, round only the final number to the precision the context needs. This tool applies exactly that discipline internally.
The second is confusing mass and weight units with force, or dry and fluid measures. A “fluid ounce” is a volume (about 29.6 mL); an “ounce” is a mass (about 28.3 g); they are unrelated despite the shared name, and recipes mix them freely. When a conversion looks surprising, check whether the two units actually measure the same physical quantity — the category tabs in the converter enforce this automatically, which is itself a quiet form of error prevention.
Where each category shows up in practice
Length — screen sizes are sold in inches everywhere, apartment listings in m² or ft² depending on the market, running distances in km or miles. The cm↔inch pair alone covers monitors, TVs, phone screens, and furniture.
Weight — international shipping quotes in kg, US shipping in lb; gym plates differ by continent; recipe portions swing between grams and ounces.
Temperature — the 37 °C / 98.6 °F body-temperature pair and the oven range (180 °C = 356 °F) are the two conversions people look up most; the reference table in the tool includes both anchors.
Data — the decimal-vs-binary split explains the eternal “missing gigabytes” complaint: a 1 TB drive holds 10¹² bytes, which Windows reports as 931 GiB using binary units. Neither number is wrong; they are different units wearing similar names.
Related tools on this site
For conversions this tool deliberately does not cover: Currency Converter handles money (rates change daily, unlike physical constants), CSS Units Converter handles px/rem/em for web work, and Timezone Converter handles the one everyday conversion where arithmetic alone fails — time.
How to Use This Tool
1
Pick a category
Choose what you are converting: length, weight, temperature, area, volume, speed, or data storage.
2
Select the units
Set the unit you have and the unit you want. The swap button reverses the direction in one click.
3
Type the value
The result updates as you type, along with a reference table of common conversions for the pair you selected.
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Essential terms and definitions related to Unit Converter.
SI Base Unit
One of the seven fundamental units of the International System (meter, kilogram, second, ampere, kelvin, mole, candela) from which all other measurement units are derived by definition.
International Yard and Pound Agreement
The 1959 treaty between six English-speaking nations that fixed the yard at exactly 0.9144 m and the pound at exactly 0.45359237 kg, making imperial-metric conversion exact rather than measured.
Binary Prefix (IEC)
The kibi/mebi/gibi prefixes (KiB, MiB, GiB) standardized by the IEC in 1998 to unambiguously denote powers of 1024, resolving the long-standing confusion with decimal kilo/mega/giga.
Frequently Asked Questions
How accurate are the conversion factors?
They are the exact legal definitions, not approximations. Since the 1959 International Yard and Pound Agreement, one inch is defined as exactly 25.4 mm and one pound as exactly 0.45359237 kg — so converting through this tool introduces no rounding error beyond the digits you choose to display. Results are computed in double-precision floating point and shown to up to 10 significant digits.
Why is temperature handled differently from other units?
Every other category converts by multiplying with a fixed factor, because those scales share a true zero. Temperature scales have offset zeros: 0 °C equals 32 °F, not 0 °F. The tool therefore applies the affine formulas (°F = °C × 9/5 + 32, K = °C + 273.15) instead of a ratio — which is also why "double the temperature" is physically meaningless in °C or °F but valid in kelvin.
Is a megabyte 1000 or 1024 kilobytes here?
Both conventions are available as separate units. KB, MB, GB and TB follow the SI decimal standard (1 MB = 1,000,000 bytes) that storage manufacturers and macOS use, while KiB, MiB, GiB and TiB follow the IEC binary standard (1 MiB = 1,048,576 bytes) that Windows and most programming contexts use. Converting between the two families shows exactly why a "500 GB" drive appears as ~465 GiB.
Why do the US and UK gallon give different results?
Because they are genuinely different units. The US gallon is defined as 231 cubic inches (about 3.785 L), while the imperial gallon used in the UK, Ireland, and Canada is defined as exactly 4.54609 L — roughly 20% larger. The converter lists them separately, which is why a '40 mpg' car in a UK review does not match a '40 mpg' figure in an American one: the miles agree, the gallons don't.
Which units should I use when sharing measurements internationally?
Metric, with the original value in parentheses if the audience is mixed — '2.5 kg (5.5 lb)'. Every country except the United States, Liberia, and Myanmar uses metric officially, and even US science, medicine, and the military work in metric internally. When a document must pick one system, metric fails the fewest readers; this converter makes producing the parenthetical value a two-second task.
Troubleshooting & Technical Tips
Common errors developers encounter and how to resolve them.
Result differs slightly from another converter site
Many converters chain rounded intermediate factors (for example using 1 mile = 1.609 km instead of the exact 1.609344 km), which compounds error across conversions. This tool converts through the exact base-unit definition in a single step, so its output is the reference value — the discrepancy is the other site's rounding.
Very large or small values display in scientific notation
Conversions spanning many orders of magnitude (nanometers to miles, bytes to terabytes) exceed what fixed decimal display can show meaningfully, so the tool switches to scientific notation (e.g. 1.609344e+12) past 10 significant digits. The value is exact; only the display format changes.
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