Unit Converter
Convert between units of length, mass, volume, area, speed, time, digital storage, pressure, energy, and temperature — instantly and fully offline.
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Disclaimer: This free tool is provided “as is,” without warranties of any kind, and is for general informational purposes only — not professional, legal, financial, medical, tax, or engineering advice. Results may contain errors; verify anything important independently and use at your own risk. We accept no liability for any loss or damage arising from its use. See our Terms of Use for details.
Step-by-Step Guide
Select a measurement category from the dropdown: length, mass, volume, area, speed, time, digital storage, pressure, energy, or temperature. Choose your From and To units using the two selectors, type your value in the input field, and the converted result and the 1-to-1 conversion rate appear instantly. Use the swap button (⇄) to reverse the From and To units without retyping.
Temperature is different from the other categories
All categories except temperature use multiplicative conversion factors — converting 5 km to miles is simply 5 × 0.621371. Temperature scales are offset as well as scaled, because the zero points differ: 0°C is not the same physical temperature as 0°F or 0K. The correct formulas are: °F = (°C × 9/5) + 32; °C = (°F − 32) × 5/9; K = °C + 273.15. This tool applies the correct formula for all three temperature pairs automatically.
Length: 5 kilometers → 3.106856 miles (factor: 1 km = 0.621371 mi). Temperature: 100 °C → 212 °F (formula: 100 × 9/5 + 32 = 212). Mass: 70 kg → 154.324 lb. Digital storage: 1 GB → 1,024 MB (binary) or 1,000 MB (decimal, SI) — the tool uses 1,024 (binary) for storage conversions as is conventional for file sizes.
Who it's for
Students, travelers, cooks, engineers, and anyone juggling metric and imperial units.
Core Features
- Ten categories: length, mass, volume, area, speed, time, digital storage, pressure, energy, and temperature.
- Two-way selection with an instant swap button and an editable value field.
- Shows a plain '1 X = N Y' rate line for quick reference.
- Accurate factor tables plus correct non-linear Celsius/Fahrenheit/Kelvin formulas.
🛡️ No tracking — your inputs, keys, and details never leave this client sandbox.
How do I convert Celsius to Fahrenheit?
Select Temperature, pick Celsius as From and Fahrenheit as To, and enter your value. The formula is °F = (°C × 9/5) + 32. The inverse is °C = (°F − 32) × 5/9. A useful mental check: 0°C = 32°F (freezing), 100°C = 212°F (boiling), and 37°C ≈ 98.6°F (normal body temperature).
What is the difference between metric and imperial units?
The metric system (SI — International System of Units) is based on powers of 10: 1 kilometer = 1,000 meters, 1 kilogram = 1,000 grams. It is used for science and in most countries for everyday life. Imperial units (used primarily in the United States, along with some legacy use in the UK) use inconsistent conversion factors: 1 mile = 5,280 feet, 1 pound = 16 ounces, 1 gallon = 128 fluid ounces. Most scientific work worldwide uses metric; US industry and consumer contexts mix both systems.
How many MB are in a GB?
In binary (IEC) convention, 1 GB = 1,024 MB, because computer memory is addressed in powers of 2. In decimal (SI) convention used by hard drive and storage manufacturers, 1 GB = 1,000 MB. This discrepancy is why a 1 TB hard drive shows as roughly 931 GB in Windows (which uses binary GiB, even though it labels them GB). This tool uses the binary convention (1 GB = 1,024 MB, 1 MB = 1,024 KB) for digital storage conversions, consistent with how operating systems report file sizes.
Does it work offline?
Yes. All conversion factors are hardcoded in the tool — no external data is fetched. You can convert units without an internet connection once the page has loaded. The only exception would be if the browser cache has been cleared.
The unit error that cost NASA $125 million
In 1999, the Mars Climate Orbiter was lost because one engineering team used metric units (newton-seconds) and another used imperial units (pound-force-seconds) in the same navigation software, with no conversion between them. The mismatch went undetected through months of operation and caused the spacecraft to enter the Martian atmosphere at the wrong angle, destroying a $327 million mission. Unit confusion is not a beginner's mistake — it is a systematic risk that affects any project where multiple parties, tools, or data sources use different measurement systems.
How experts approach unit conversion differently than beginners
Beginners convert one number at a time when they need to. Experts embed unit awareness into their workflow from the start. They label every number with its unit in notes and code comments so the unit travels with the value. They use dimensional analysis — treating units as algebraic quantities that multiply and cancel — to verify that a formula produces the right unit for the output. When a formula gives meters-squared where you expected meters, dimensional analysis catches the error before it becomes a $125 million problem. They also know which conversions are exact (1 inch = 25.4 mm exactly, by definition) and which are approximations (1 mile ≈ 1.609344 km, which is exact by international agreement but often rounded in practice).
Temperature is structurally different from every other unit
All unit conversions except temperature use a single multiplicative factor: 1 km = 0.621371 miles, so N km × 0.621371 = N miles. Temperature scales are offset as well as scaled because their zero points represent different physical temperatures. 0°C is not 0°F — it is 32°F. The correct Celsius-to-Fahrenheit formula is °F = (°C × 9/5) + 32; simply multiplying by a factor gives a wrong answer. The Kelvin scale avoids this problem because it places zero at absolute zero (−273.15°C), making it a ratio scale where doubling the Kelvin value genuinely means twice the thermal energy — a property Celsius and Fahrenheit lack.
The binary vs. decimal gigabyte problem
Digital storage adds another layer of confusion: the word "gigabyte" means different things depending on context. Operating systems and programming languages traditionally use binary prefixes (1 GB = 1,024 MB = 2^30 bytes). Hard drive manufacturers use decimal prefixes (1 GB = 1,000 MB = 10^9 bytes). A 1 TB hard drive advertised by a manufacturer shows as 931 GiB in Windows because the OS reports in binary gibibytes. This tool uses the binary convention (1 GB = 1,024 MB) consistent with how operating systems report file sizes.