Everyday calculators
A scientific calculator plus percentages, ratios and unit conversions for the calculations people actually do between larger financial decisions.
- Percentage calculatorFind a percentage of a number, reverse a percentage, or calculate percentage increase, decrease and difference.
- Discount calculatorWork out the dollar saving and sale price from a percentage off.
- Length converterConvert millimetres, centimetres, metres, kilometres, inches, feet, yards and miles.
- Weight converterConvert milligrams, grams, kilograms, tonnes, ounces, pounds and stone.
- Volume converterConvert millilitres, litres, Australian metric cups and spoons, and US or imperial fluid ounces and gallons.
- Temperature converterConvert Celsius, Fahrenheit and Kelvin. Weather and cooking in Australia use Celsius.
- Area converterConvert mm², cm², m², hectares, km², square feet, square yards and acres.
- Scientific calculatorEvaluate expressions with sin, cos, tan, logs, powers, roots, π, e and factorials. Switch between degrees and radians.
Not every calculation is a financial decision. Most are small: a percentage off a price, a unit conversion from a recipe or a product spec, a quick piece of arithmetic you would rather not do in your head.
The tools here handle those, and they show their working. The percentage calculator in particular covers the cases people mix up — a percentage of a number, a percentage increase, and the difference between the two, which are three different questions with three different answers.
Which tool do you need?
- Any percentage question — of, increase, decrease, or the difference between two numbers: use the percentage calculator.
- Working out a sale price or the saving on a discount: use the discount calculator.
- Pricing something to hit a target margin: use the margin and markup calculator, which shows why a 25% markup is a 20% margin.
- Converting length, weight, volume, area or temperature: use the matching converter.
- Anything involving powers, roots, logarithms or trigonometry: use the scientific calculator.
Common questions
What is the difference between a percentage increase and a percentage difference?
A percentage increase is measured against the original value, so going from 40 to 50 is a 25% increase. A percentage difference is measured against a reference or an average, which is why the same pair of numbers can be described as a 20% decrease going the other way.
Why is a 25% markup not a 25% margin?
Markup is calculated on cost and margin is calculated on the selling price. A $100 item marked up 25% sells for $125, and the $25 profit is 20% of that $125 selling price. The margin is always the smaller number.
Are the unit conversions exact?
The conversion factors are the SI and internationally agreed definitions, so they are exact where the definition is exact — an inch is exactly 25.4 mm, for example. Displayed results are rounded for readability, and the page states the factors used.
Before you rely on a result
Every calculator on this page shows the formula it used, the assumptions it made and the source of any regulated figure. Results are estimates and not professional advice — the disclaimer explains the limits, and the guides explain the reasoning in more depth.