Calculator

Scientific, percentage, BMI, date and unit conversion — all on one page.

The angle unit is currently Deg. You can also type with your keyboard: Enter calculates and Esc clears. Results are rounded to 13 significant digits, so calculations beyond 15 digits may show a small rounding error.

× % = ?

of which is what %?

changes to what % change?

changes by % = ?

The four rows are independent — only the rows you fill in show a result. Enter a negative value in the last row to calculate a decrease.

Male Female

Units

Height

Weight

Body Mass Index

Body Mass Index is your weight in kilograms divided by the square of your height in metres. The categories shown follow the World Health Organization classification used in most Western countries. BMI does not distinguish muscle from fat, so treat it as a rough indicator and consult a healthcare professional for a real assessment. Imperial input is converted at 1 inch = 2.54 cm and 1 pound = 0.45359237 kg.

Start date

End date

Base date

Amount

Unit

The days-between calculation shows both the plain difference and the inclusive count. Today and tomorrow are 1 day apart, but counting today as day one makes it 2 days. When adding months, the end of the month is clamped: 31 January plus one month gives 28 February (29 in a leap year).

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Results update as you type or change a unit. The list below shows the same value converted into every unit in that category. Data sizes use 1 KB = 1,024 bytes.

What each tool does

Scientific calculator

Handles arithmetic and parentheses along with trigonometry (sin, cos, tan), inverse trigonometry, natural and base-10 logarithms, square roots, powers and factorials. The Rad·Deg key switches the angle unit, and Inv turns the trigonometric keys into their inverses.

Ans recalls the previous result so you can chain calculations without retyping. EXP enters a power of ten, so 2 EXP 5 means 200,000. Everything is parsed with a proper expression parser, which means normal operator precedence applies: 1 + 2 × 3 gives 7, not 9.

Percentage calculator

Four separate questions, because percentage problems are easy to get backwards. What is X percent of a number, what percentage one number is of another, the percentage change between two values, and the result after applying a percentage change.

Useful for discounts, tips, tax, markup, growth rates and exam scores. The last row accepts negative numbers if you want to calculate a decrease.

BMI calculator

Enter your height and weight in either metric or imperial units and the calculator shows your body mass index, the category it falls into, and the weight range that would put you in the healthy band.

Categories follow the WHO classification. Note that many Asian countries use lower thresholds — in Korea and Japan the obesity cut-off starts at 25 rather than 30, so the same number can be classified differently depending on where you are.

Date calculator

Find the number of days, weeks and months between two dates, broken down into years, months and days. Or take a base date and move forward or backward by a number of days, weeks, months or years — the result includes the day of the week.

Handy for deadlines, contract terms, countdowns, notice periods and age calculations. Month arithmetic clamps to the end of the month so results stay on a real calendar date.

Unit conversion categories

Ten categories are supported, covering both metric and US customary or imperial units.

Length — millimetre to kilometre, inch, foot, yard, mile, nautical mile
Area — square metre, are, hectare, square foot, acre, square mile
Weight — gram, kilogram, tonne, ounce, pound, stone
Volume — litre, cubic metre, US and imperial gallon, quart, pint, fluid ounce
Temperature — Celsius, Fahrenheit, Kelvin, Rankine
Pressure — pascal, bar, atmosphere, mmHg, inHg, psi
Speed — m/s, km/h, mph, knot, Mach
Fuel economy — mpg (US and imperial), km/L, L/100km
Data — bit, byte, kilobyte through petabyte
Time — millisecond through year

Two details are worth knowing. The US and imperial gallon are not the same: a US gallon is 3.785 litres while an imperial gallon is 4.546 litres, which is why US and UK miles per gallon figures differ by about 20 percent for the same car. And Fahrenheit and Celsius are not a simple ratio — they have different zero points, which the converter accounts for.

Frequently asked questions

Why does L/100km move in the opposite direction?

Miles per gallon and km/L measure distance per unit of fuel, so higher is better. L/100km measures fuel per fixed distance, so lower is better. They are reciprocals of one another, and the converter handles that inversion correctly.

Is anything I enter stored?

No. Every calculation runs inside your browser. Nothing is sent to a server or saved anywhere. Refresh the page and all inputs are gone.

Can I link straight to one tool?

Yes. Add #bmi, #date, #unit or #pct to the end of the address and that tab opens directly. The address updates as you switch tabs, so you can copy it and share it.

How accurate are the results?

The scientific calculator rounds to 13 significant digits. Because computers store decimals in binary, calculations beyond about 15 digits can show a tiny rounding error. This has no practical effect on everyday use.