Convert anything, instantly.

How to use the converter

Pick a category from the tabs, choose your two units, and type a number into the left box. The result appears instantly — nothing to submit and nothing to wait for. The swap button in the middle flips the direction, Copy puts the result on your clipboard with its unit attached, and any tile in the Quick reference row loads that conversion straight into the converter.

There are nine categories: cooking, temperature, length, weight, volume, area, speed, data size and time.

Why a cup of flour and a cup of sugar don't weigh the same

This is the single most common source of baking failures, and it comes down to a simple mismatch: a cup measures volume, a gram measures weight. There is no universal cup-to-gram figure, because the answer depends entirely on what's in the cup.

A cup of all-purpose flour weighs around 125 g. A cup of granulated sugar weighs around 200 g — sixty percent more — because sugar crystals are dense and pack tightly, while flour is light and holds a lot of air. Honey, at roughly 340 g per cup, is nearly three times the weight of the same volume of flour.

Worse, flour doesn't even weigh the same as itself. Scooping the cup directly into the bag compresses the flour and can give you 20% more than spooning it in loosely and levelling the top with a knife. On a large bake that's an entire extra half-cup you never intended to add, which is why so many cakes come out dry for no obvious reason.

If you bake regularly, a digital kitchen scale is the fix. Weigh in grams and the ambiguity disappears completely. Until then, use the ingredient-specific options in the cooking category rather than a generic cup conversion, and spoon-and-level rather than scoop.

Not every cup is the same size

A recipe written in Sydney and one written in Seattle can both say "1 cup" and mean different amounts. The American customary cup is 236.6 ml. The metric cup used in Australia, New Zealand and Canada is 250 ml. British recipes from before metrication may use an imperial cup of 284 ml, and a Japanese cup is 200 ml.

The same split runs through fluid ounces and gallons. A US fluid ounce is 29.57 ml while a UK one is 28.41 ml, and a US gallon is 3.785 litres against the imperial gallon's 4.546 — a difference of about 20%, which is enough to matter for anything from a punch recipe to a fuel-economy figure. This converter defaults to US customary units and lists imperial ones separately where they differ.

KB vs KiB — why a 1 TB drive shows up as 931 GB

Buy a 1 TB drive, plug it in, and Windows tells you it's 931 GB. Nothing is missing and nobody is cheating you — two different counting systems are being used at once.

Storage manufacturers use decimal units, where a kilobyte is 1,000 bytes and a terabyte is a clean 1,000,000,000,000. Operating systems historically use binary units built on powers of two, where the equivalent step is 1,024. The correct names for the binary units are kibibyte, mebibyte and gibibyte (KiB, MiB, GiB), but Windows labels them KB, MB and GB anyway, which is where the confusion comes from. Divide a decimal terabyte by a binary one and you land on 931.

macOS and Linux both switched to decimal reporting years ago, so the same drive reads as 1 TB there. The data category above converts between both systems, so you can check what a figure really means.

Where these numbers come from

Most of the conversions on this page aren't approximations — they're exact by definition. Under the 1959 international yard and pound agreement, one inch is precisely 25.4 mm and one pound is precisely 0.45359237 kg. Everything else in the length and weight categories derives from those two figures. Temperature, area, speed, time and data conversions are similarly exact, and results are rounded for display rather than in the calculation.

Cooking is the exception, and deliberately so. Ingredient weights are averages drawn from standard baking references, because there is no exact answer to what a cup of flour weighs — only a sensible one. Treat those figures as reliable starting points, not physical constants.

Everything runs on your device

The converter is plain JavaScript running in your browser. Nothing you type is uploaded, logged or stored, and once the page has loaded it keeps working without a connection. That's the same approach as the rest of Filesmith — our file converter and image editor process files locally too, so your documents and photos never leave your machine.