Online Calculators & Converters
These calculators cover questions that come up at work, in the shop and at home: what a discount really saves, whether a price leaves enough margin, how many days lie between two dates, or what a regular saving might grow to.
Each calculator shows the formula it uses and explains its assumptions, so you can check the arithmetic yourself rather than trusting a number you cannot see behind.
The 8 tools in this category
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Percentage Calculator
Solve the five most common percentage questions, with formulas. -
Discount Calculator
Work out sale prices, savings, stacked discounts and tax. -
Profit Margin Calculator
Find margin, markup and the selling price that hits your target. -
Age Calculator
Find an exact age in years, months and days on any date. -
Date Difference Calculator
Count days and working days between dates, or add days to a date. -
Unit Converter
Convert length, weight, temperature, volume, data and more. -
BMI Calculator
Calculate adult body mass index in metric or imperial units. -
Compound Interest Calculator
Project how savings grow with compound interest and deposits.
Accuracy and rounding
Calculations use standard double-precision arithmetic and results are rounded only for display. Where rounding can matter — for money, for example — the result shows two decimal places and the explanation states how the figure was reached. Date calculations follow the real calendar, including leap years and months of different lengths.
These tools are for general information. Financial results such as those from the Compound Interest Calculator are projections based on a fixed rate and do not account for taxes, fees or changing interest rates. The BMI Calculator provides a screening measure, not a health assessment.
Business and everyday calculations
For pricing work, the Profit Margin Calculator works out margin, markup and selling price from whichever two values you know, while the Discount Calculator handles single and stacked discounts. The Percentage Calculator answers the five most common percentage questions, including percentage change.
For dates and measurements, use the Age Calculator, the Date Difference Calculator and the Unit Converter, which covers length, weight, temperature, area, volume, speed, data and time.