Free Unit Converter & Measurement Calculator
Convert 200+ units of length, weight, temperature, volume, digital storage, energy, and more — instantly in your browser. No sign-up, no tracking, no ads.
Featured Converter
Convert between kilometers and miles — the most searched conversion on M-Convert.
Popular Conversions
The conversions our visitors use most often.
Kilometers to Miles
Convert km to mi with the exact factor 0.621371192237334.
Celsius to Fahrenheit
Temperature conversion using °F = °C × 9/5 + 32.
Kilograms to Pounds
Mass conversion using 1 kg = 2.204622621848776 lb.
MB to MiB
Decimal SI megabytes vs binary IEC mebibytes.
Meters to Feet
Exact conversion: 1 m = 3.280839895013123 ft.
Inches to Centimeters
Exactly 1 in = 2.54 cm by international agreement.
Liters to Gallons
US liquid gallons and imperial gallons both supported.
km/h to mph
Vehicle speed conversion using 0.621371 factor.
Browse by Category
All 200+ converters are organized into clear topic groups.
Basic Conversions
Length, weight, volume, temperature, area, time, speed.
20 toolsComputer & Digital
Data storage, transfer speed, bases, ASCII, DPI.
20 toolsElectrical & Electronics
Voltage, current, resistance, capacitance, inductance.
15 toolsScience & Physics
Viscosity, entropy, radiation, photometry, molarity.
25 toolsConstruction & Engineering
Concrete, rebar, slope, stress, board feet, gear ratios.
20 toolsCooking & Food
Cups, grams, tablespoons, butter, flour, temperature.
10 toolsGeography & Weather
Nautical miles, knots, coordinates, time zones, altitude.
15 toolsFashion & Lifestyle
Shoe size, clothing, ring size, fabric GSM, paper sizes.
15 toolsAutomotive
Fuel economy, MPG, horsepower, tire pressure, torque.
15 toolsMedical & Chemistry
Glucose, cholesterol, molarity, ppm, dosage units.
15 toolsMathematics
Fractions, decimals, percentages, bases, roman numerals.
15 toolsAstronomy & Advanced
Light-years, parsecs, Planck units, Mach, c.
15 toolsWhy M-Convert
Built for accuracy, speed, and trust — with no compromises.
Verified Mathematics
Every conversion factor is drawn from the SI Brochure, NIST SP 811, or IEEE 1541. Exact relationships are never approximated.
Instant & Offline
All conversions run locally in your browser. No network requests, no waiting, no dependency on external services.
Private by Design
No accounts, no cookies, no tracking. Your conversions never leave your device. Recent history is stored locally and can be cleared anytime.
Conversion Guides
Learn the theory behind the numbers — from SI prefixes to significant figures.
SI vs. Customary Units
How the metric system and imperial/US customary systems differ, and where each is used.
Significant Figures & Rounding
Why 1 km ≠ 0.6214 mi in every context, and how to round correctly.
Binary vs. Decimal Data Units
Why a "1 TB" drive shows up as "931 GB" in your OS, and what MiB really means.
Frequently Asked Questions
Is M-Convert free to use?
Yes. Every converter and calculator on M-Convert is completely free with no account, no trial period, and no hidden paywall.
Do you store the values I convert?
No. All calculations run entirely in your browser. Nothing is transmitted to any server. Your recently used converters may be saved locally on your device using localStorage, and you can clear them at any time from Recent tools.
How accurate are the conversions?
Exact relationships — such as 1 inch = 2.54 centimeters or 1 mile = 1.609344 kilometers — are used exactly as defined. Other constants are drawn from the SI Brochure and NIST SP 811 with documented precision. See our Accuracy & Methodology page for details.
What is the difference between MB and MiB?
MB (megabyte) is a decimal SI unit equal to 106 bytes = 1,000,000 bytes. MiB (mebibyte) is a binary IEC unit equal to 220 bytes = 1,048,576 bytes. This is why an operating system may display a 1 TB drive as roughly 931 GiB.
Can I use M-Convert offline?
Once a page has loaded, all conversions continue to work without an internet connection. You can also install M-Convert as a PWA from your browser menu for a dedicated app experience.
Which units does the temperature converter support?
Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R). Each conversion uses explicit forward and reverse formulas so there is no loss of accuracy even at extreme values.
Ready to convert?
Browse all 200+ tools, or jump straight to the category you need.