Using the calculators
Choose the calculator that matches your question. Check the unit beside each field and replace the example values with your own. Select Calculate to see the result. The formula, a worked example and the limits of the model appear on the same page.
Numbers and rounding
Individual number fields use a decimal point: 1.234 means one point two three four. You may group thousands with commas or spaces, for example 1,234.56 or 1 234.56. A comma is only accepted in a valid group of three digits; use a point for decimals. Scientific notation such as 1e-6 is supported. For lists and tables, follow the instructions beside the field. Calculations use unrounded values internally; rounding is applied when displaying the result. Very small or very large results appear in scientific notation.
Calculations across countries
The English edition contains general mathematics, unit conversions and practical planning models. Amounts, prices and interest rates are example inputs. Use the same currency throughout a calculation. National salary and tax rules, social benefits, public holiday calendars, official inflation series, news and current lottery results are outside this catalogue.
Models and sources
Each calculator states its formula and assumptions. Technical and scientific explanations refer to sources such as BIPM, IUPAC or OpenStax where relevant. A simplified model cannot fully account for measurement error, material properties or individual contract terms.
Saving and sharing
Calculations run in your browser. The Share input link button places your values in the part of the address after #. Anyone who receives the complete link can read those inputs. A CSV export or a copied result is created when you use the corresponding button.
Reporting a problem
Please include the calculator address, a simple example and the result you expected when reporting a problem. The contact page gives the operator’s email address.