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Convert length, mass, temperature, volume, area, speed, pressure, energy, data and angle — with Australian cooking measures listed separately, because a tablespoon here is 20 mL.
| Unit | Value |
|---|
This is the conversion that catches people most often, and it is not in most converters at all.
| Measure | Australia & NZ | United States | United Kingdom |
|---|---|---|---|
| Tablespoon | 20 mL | 14.79 mL | 15 mL |
| Teaspoon | 5 mL | 4.93 mL | 5 mL |
| Cup | 250 mL | 240 mL | 250 mL (metric) |
The converter above lists both, labelled, so you can pick the one your recipe actually meant. As a rule of thumb: if the recipe is Australian, a tablespoon is 20 mL. If it comes from anywhere else, assume 15 mL — and if a recipe specifies "3 teaspoons" where you would expect a tablespoon, that is usually a sign the author knew about this problem.
Australia adopted the metric system through the 1970s, and the changeover was thorough — roads, weather, shops and schools all switched within a few years. But imperial units did not vanish, and knowing where they survive explains most of the conversions people actually need.
| Where imperial survives | Why |
|---|---|
| Older houses | Built to imperial dimensions — 8-foot ceilings, timber in feet and inches |
| Plumbing and fittings | Pipe threads are still commonly sized in inches |
| Screens and wheels | A 55-inch TV and 18-inch wheels, worldwide |
| Aviation and marine | Feet for altitude, nautical miles and knots for distance and speed |
| Some recipes | Ounces and Fahrenheit in older or imported cookbooks |
| Body measurements | Plenty of people still think in feet, inches and stone |
Every category here works the same way: convert to a base unit, then out to the target. It is worth understanding because it explains why temperature behaves differently.
| Category | Base unit |
|---|---|
| Length | metre |
| Mass | kilogram |
| Volume | litre |
| Area | square metre |
| Speed | metre per second |
| Pressure | pascal |
| Energy | joule |
| Temperature | degree Celsius — but see below |
Every other conversion is a simple multiplication, because the scales all start at the same place: zero metres is zero feet, zero kilograms is zero pounds.
Temperature scales do not share a zero. Zero Celsius is 32 Fahrenheit. So converting needs an offset as well as a ratio, and no single multiplier will do it.
| Reference point | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| A cool Melbourne day | 15 | 59 | 288.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| A hot Australian day | 40 | 104 | 313.15 |
| Water boils | 100 | 212 | 373.15 |
For a quick mental estimate, doubling the Celsius figure and adding 30 gets you close: 20 °C becomes roughly 70 °F, against a true 68. It drifts at the extremes but it is fine for weather.
| Conversion | Exact | Close enough |
|---|---|---|
| Inch to mm | 25.4 exactly | 25 |
| Foot to metres | 0.3048 exactly | 0.3 |
| Mile to km | 1.609344 exactly | 1.6 |
| Pound to kg | 0.45359237 exactly | 0.45 |
| Stone to kg | 6.35029318 | 6.35 |
| Litre to US gallon | 0.264172 | 0.26 |
| Litre to UK gallon | 0.219969 | 0.22 |
| km/h to mph | 0.621371 | divide by 1.6 |
| Knot to km/h | 1.852 exactly | 1.85 |
| Hectare to acres | 2.47105 | 2.5 |
Data storage has the same problem as the tablespoon — one name, two meanings.
| Binary | Decimal | |
|---|---|---|
| 1 KB | 1,024 bytes | 1,000 bytes |
| 1 MB | 1,048,576 bytes | 1,000,000 bytes |
| 1 GB | 1,073,741,824 bytes | 1,000,000,000 bytes |
| Used by | Windows file sizes, RAM | Storage vendors, macOS, network speeds |
The gap is 7.4% at gigabyte scale, which is why a 1 TB drive shows as about 931 GB in Windows — the drive holds a decimal terabyte and Windows divides by 1,024 while still writing "GB". The converter offers both, labelled. Our bandwidth calculator goes into what this does to download time estimates.
| Situation | What you usually need |
|---|---|
| Overseas recipes | Cups, tablespoons and °F — check which country's spoons |
| Renovating an older house | Feet and inches to millimetres. Australian building works in mm |
| Buying tools or timber | Imperial sockets and drill bits alongside metric |
| Reading a US car review | mph to km/h, and miles per gallon to L/100km |
| Land and property | Acres to hectares — older titles often use acres |
| Personal measurements | Feet and inches to centimetres, stone to kilograms |
| Tyre and wheel sizes | Rim diameter in inches, tyre width in millimetres — on the same tyre |
How many mL is an Australian tablespoon?
Twenty millilitres — four teaspoons. Australia and New Zealand are among very few countries using a 20 mL tablespoon; the United Kingdom and most of Europe use 15 mL and the United States about 14.79 mL. It matters in cooking, because three Australian tablespoons is 60 mL against roughly 44 mL for three American ones.
How many mL is an Australian cup?
250 mL, the same as the metric cup used in the UK and New Zealand. The American cup is 240 mL, so a US recipe converted straight across gives you about 4% more of everything. For most baking that is tolerable; for anything where the ratio of liquid to flour matters, it is worth adjusting.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32, so 20 °C becomes 68 °F. Going the other way, subtract 32 then multiply by 5/9. For a rough mental estimate, double the Celsius figure and add 30 — that gives 70 for 20 °C, close enough for weather. The two scales meet at exactly −40.
Why is temperature converted differently from other units?
Because temperature scales do not share a zero point. Zero metres is zero feet, so length converts with a single multiplication. Zero Celsius is 32 Fahrenheit, so converting needs an offset as well as a ratio. Kelvin is the exception among temperature scales — it starts at absolute zero, so it relates to Celsius by a simple addition of 273.15.
When did Australia switch to metric?
During the 1970s, in a coordinated national programme covering roads, weather, retail, construction and education. The changeover was unusually quick and complete by international standards. Imperial units survive in specific places — older houses and plumbing, screen and wheel sizes, aviation and marine navigation, and plenty of people's mental picture of their own height and weight.
Is an inch exactly 25.4 mm?
Yes, exactly. Under the international yard and pound agreement of 1959, the inch is defined as precisely 25.4 millimetres and the pound as precisely 0.45359237 kilograms. Imperial units are now defined in terms of metric ones, which means conversions between them can be exact rather than approximate.
What is the difference between a US and UK gallon?
A UK imperial gallon is 4.546 litres and a US gallon is 3.785 litres — the American one is about 20% smaller. This makes any fuel economy figure quoted in miles per gallon ambiguous without knowing which gallon is meant, and it is one reason Australia uses litres per 100 kilometres instead.
How do I convert miles per gallon to L/100km?
Divide 235.215 by the US mpg figure, or 282.481 by a UK mpg figure. A car rated at 30 US mpg uses about 7.8 L/100km. Note that the two scales run in opposite directions — a higher mpg is better, while a lower L/100km is better — so they cannot be compared by eye.
How many kilograms is a stone?
One stone is 6.35029318 kilograms, or 14 pounds. So 12 stone is about 76.2 kg. The stone is still used conversationally in Australia and the UK for body weight, though almost never in medical or official contexts.
Why does my hard drive show less space than advertised?
Because the manufacturer counts in decimal and Windows counts in binary. A 1 TB drive holds one trillion bytes exactly as advertised, but Windows divides by 1,024 three times and arrives at about 931 — while still labelling the result "GB". Nothing is missing; the two systems simply count differently.
How do I convert square feet to square metres?
Multiply by 0.09290304, so 1,000 square feet is about 92.9 square metres. Note that the area factor is the length factor squared — 0.3048 metres per foot becomes 0.09290304 for square feet. The same applies to volume, where the factor is cubed.
Can I convert temperature below absolute zero?
No, and the calculator will tell you so. Absolute zero is −273.15 °C, −459.67 °F or 0 K, and it is the lowest temperature physically possible. Any input that would produce a result below it is flagged rather than converted, since the answer would be meaningless.
Most unit conversion is mechanical — multiply, divide, done. The parts worth paying attention to are the ones where a single word means two different things: the tablespoon, the gallon, and the gigabyte.
For a single measurement type there are dedicated pages — the length, weight, temperature and cooking converters each go further than this hub does.
Australia sits awkwardly across several of these, using a metric system with a distinctive tablespoon, an imperial past that survives in older houses, and international standards that use feet for altitude and inches for wheels. The converter above handles all of it — the important thing is knowing which unit you actually meant.