Convert Any Unit Instantly
Length, weight, temperature, volume, area, speed, time, and digital storage — 8 categories in one tool. No sign-up, works in your browser.
Everything You Need for Unit Conversion
Bidirectional, Real-Time
Type in either field and the other updates instantly — no separate "convert" button, no page reload.
8 Categories, 45+ Units
Length, weight, temperature, volume, area, speed, time, and digital storage — from millimeters to miles, bits to terabytes.
Accurate Temperature Math
Celsius, Fahrenheit, and Kelvin use proper formula conversion, not a simple multiplier — the math is actually correct.
Quick-Reference Table
Every category shows a full reference table of common conversions, so you don't even need to type a number.
100% Private
All conversion happens in your browser. Nothing you type is sent to a server, logged, or tracked.
Works Anywhere
Fully responsive on mobile, tablet, and desktop. Use it on any device without installing anything.
Unit Converter
How to Use UnitFlip
Pick a Category
Choose length, weight, temperature, volume, area, speed, time, or digital storage from the tabs above.
Type a Value
Enter a number in either field — the other side converts instantly. Change units with the dropdowns.
Swap or Copy
Flip the direction with the swap button, or copy the result straight to your clipboard.
How Unit Conversion Actually Works
Most unit conversion is just multiplication. Every unit in a category — length, weight, volume, area, speed, time, digital storage — has a fixed conversion factor relative to a base unit (meters for length, kilograms for weight, and so on). To convert 5 miles to kilometers, you multiply 5 by 1.609344 — the number of kilometers in one mile. Convert to the base unit, then divide by the target unit's factor.
Temperature is the exception. Celsius, Fahrenheit, and Kelvin don't share a common zero point — 0°C is 32°F, not 0°F — so converting between them needs an actual formula (°F = °C × 9/5 + 32) rather than a simple multiplier. UnitFlip handles this correctly instead of treating temperature like every other unit.
Digital storage has its own wrinkle: a kilobyte is ambiguous. This tool uses the binary convention (1 KB = 1024 bytes) that operating systems report, rather than the decimal convention (1 KB = 1000 bytes) that storage manufacturers print on the box — see the FAQ below for why that matters.
Frequently Asked Questions
What unit categories does this converter support?
Eight categories: Length (mm to miles), Weight/Mass (mg to stone), Temperature (Celsius, Fahrenheit, Kelvin), Volume (mL to gallons), Area (cm² to acres), Speed (m/s to knots), Time (milliseconds to years), and Digital Storage (bits to terabytes).
Why does temperature need a formula instead of just multiplying?
Length, weight, and most other units share a common zero point, so converting is just multiplication by a fixed factor. Temperature scales don't share a zero — 0°C is 32°F, not 0°F — so each conversion needs its own formula: °F = °C × 9/5 + 32, °C = (°F − 32) × 5/9, K = °C + 273.15.
Is a kilobyte 1000 bytes or 1024 bytes?
Technically ambiguous, and a common source of confusion. Storage manufacturers use decimal (1 KB = 1000 bytes), while operating systems traditionally use binary (1 KB = 1024 bytes, more precisely called a kibibyte or KiB). This converter uses the binary convention (1024), matching what Windows, macOS, and most software report.
What's the difference between a US gallon and an Imperial gallon?
An Imperial (UK) gallon is about 20% larger than a US gallon — 4.546 liters versus 3.785 liters. This converter uses US customary units (gallon, quart, pint, cup, fluid ounce) since they're the more commonly searched default; switch to Liters if you need a unit that's the same everywhere.
How accurate are the conversions?
All conversion factors use standard internationally-defined values (e.g. 1 inch = exactly 25.4 mm, 1 pound = exactly 0.45359237 kg) with double-precision floating point math, then displayed rounded to a readable number of decimal places.
Does this tool send my data anywhere?
No. All conversion math runs in JavaScript directly in your browser. Nothing you type is sent to a server, logged, or stored.