About & methodology
Calcapedia is a collection of free online calculators for everyday questions about math, money, health, dates, and measurements. The goal is simple: give a correct answer quickly, and explain it well enough that you can trust it.
How calculators are built
- Each calculation is written as its own small, explicit function — no formula is assembled from text or evaluated at runtime.
- Inputs are validated before anything is calculated. Undefined cases, such as dividing by zero, produce a clear message instead of a misleading number.
- Every calculator has automated tests with known reference values, zero and negative values where they make sense, invalid input, rounding, and formula-specific edge cases like leap years or impossible triangles.
- Unit conversions use exact internationally defined factors; date arithmetic works on calendar days so results don't shift with time zones.
What we publish alongside each result
Every calculator page explains what the tool does, what each input means, the formula, a worked example, how to read the result, and the assumptions and limitations behind it. Finance and health tools carry extra notes, because those results are estimates and are not a substitute for professional advice.
Grade levels, standards and worksheets
Many calculator pages show the school grade at which their math is usually taught and, where one genuinely applies, the matching Common Core State Standards for Mathematics code, linked to the official standard. Calculators whose math goes beyond high school are marked as college level. Each of these pages also lists real-world uses of the idea behind it.
Most calculators offer a printable worksheet of practice problems with an answer key. Every answer and worked step comes from the same tested code as the calculator, and the seed printed on each sheet rebuilds the identical sheet later.
Common Core State Standards: © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved. The standards are cited for reference; Calcapedia is not affiliated with or endorsed by their owners.
Solving it on a calculator
Many pages show the keys to press to get their worked-example answer on a basic, scientific, graphing or financial calculator. An automated test presses every key on this site's own calculators and checks the answer against the page's calculation.
Some pages also have steps for a named calculator model. Those follow the model's official guidebook, cited by page next to the steps, and are replayed on a simulation of the documented behaviour; they have not been tried on the physical calculator. The instructions are our own words, with no logos, pictures or text from the guidebook.
Calcapedia is independent and is not affiliated with or endorsed by Texas Instruments. TI and BA II Plus are trademarks of their owners and are used here only to say which calculator these steps are for.
Calcapedia is independent and is not affiliated with or endorsed by Texas Instruments. TI and TI-84 Plus CE are trademarks of their owners and are used here only to say which calculator these steps are for.
Calcapedia is independent and is not affiliated with or endorsed by Texas Instruments. TI, TI-30XS MultiView and MathPrint are trademarks of their owners and are used here only to say which calculator these steps are for.
Corrections
If you believe a result is wrong, please let us know with the inputs you used and the answer you expected. Corrections are tested and noted with the page's update date.