Convert Tools

Twenty-six converters for the numbers that are a table, not a formula

A metre is defined and a cup is not. A kilogram is defined and a size 40 shoe is not. Everything here converts a published convention rather than a physical quantity, which is why each of these tools says *which* convention it used — and why the honest ones say that the number they gave you is where to start rather than what to order.

A size is not a measurement. Shoe, clothing, ring and bra sizes were set by makers who disagreed with each other, every maker adjusts them, and the same nominal size differs by a whole step between two shops on the same street. Every size tool here gives the measurement the size was derived from, because that is the only number in the answer that means anything on its own.

The unit that seems to have one meaning has several. A cup is four different volumes, a tablespoon three, a gallon two, a gigabyte two, a mile per gallon two. The system is chosen rather than guessed and the answer says which was used, because a recipe almost never says and the difference between a US and an imperial pint ruins a batter.

A density is a range, and the range is the answer. Flour scooped from the bag is a fifth heavier than flour spooned and levelled, and no converter can know which was done. The tools that turn a volume into a weight give the spread as well as the middle, which is the reason serious baking books ask for grams.

Kitchen

Cooking Measurement Converter
Cups, spoons, millilitres and ounces, with the system stated.

Grams to Cups
Weight and volume for fifty ingredients, with the spread each one has.

Oven Temperature Converter
Celsius, Fahrenheit and gas marks, with the fan adjustment stated.

Baking Pan Converter
Two tins compared by volume, with the batter and the timing adjusted.

Recipe Scaler
Every line multiplied, and the lines that do not multiply named.

Sizes you wear

Shoe Size Converter
A foot length in every national scale, with the widths as well.

Clothing Size Converter
One measurement on six scales, and the letter that covers several.

Ring Size Converter
A finger measured around or across, on six scales.

Bra Size Converter
A band and a cup on six scales, with the sister sizes named.

Hat and Glove Size Converter
The two sizes that really are a measurement, in every scale.

Screen and paper

Paper Size Reference
Every sheet in millimetres, inches, points and pixels.

Pixels, Rems and Points
A column of lengths in every unit a stylesheet uses.

Pixel Density Calculator
Resolution and diagonal into pixels per inch, dot pitch and distance.

Print Size Calculator
How big an image prints, and how big it prints well.

Screen Size Calculator
What a diagonal actually buys, and what a second screen buys.

Data Transfer Time
How long a file takes over a line, with bits and bytes kept apart.

Bit Rate and File Size
A recording's size from its rate, or the rate that fits a size.

Garage and workshop

Fuel Economy Converter
An economy in every unit, and what a trip costs at it.

Tyre Size Calculator
A marking read out in millimetres, with a second size beside it.

Wire Gauge Converter
A gauge into a diameter, a cross-section and a resistance.

Screw Size Converter
A thread's pitch, its tapping drill and its clearance hole.

Notations

Coordinate Format Converter
A place written three ways, and what each decimal place is worth.

Timesheet Hours Converter
Hours and minutes against decimal hours, totalled and rounded openly.

Speed and Pace Converter
A pace or a speed in every form, with the finish times that follow.

Roman Numeral Date
A date in numerals, read both ways, and honest about the notation.

Battery Capacity Converter
Milliampere-hours into watt-hours, at a voltage that has to be stated.

Questions

Why does every answer say which table it used?: Because the tables disagree. A US cup is 236.6 ml, a US legal cup 240, a metric cup 250 and an imperial cup 284.1; a British bra cup letter above D is not the American one; a men's and a women's UK shoe size start from different zeros. A single number with no scale attached is the commonest way these conversions go wrong.
Are the sizes accurate?: They are the published charts, and the published charts are indicative. Makers adjust them; clothing numbers have drifted downwards for decades; a shoe last differs between two lines from the same factory. Use the measurement, and the size as a starting point.
Which numbers here are exact?: More than you might expect, and each says so. An inch is 25.4 mm by definition, a US gallon is 231 cubic inches, a CSS pixel is a fixed ninety-sixth of an inch, the ISO paper series follows from three root sheets and one rounding rule, and an American wire gauge is a geometric progression between two defined diameters. Those conversions are exact. A density, a rolling circumference and a size chart are not, and those say that instead.
Do the tools work on a phone?: Yes. The whole interface lays out from a phone held upright to a desktop, and the drawings — two baking tins to scale, two tyres side by side — scale with it.

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