Anirban Kundu — Creator & Editor, CalculatorBin

I build every calculator on CalculatorBin and check every one before it goes live. For twenty years my job has been teaching science and physics in school — explaining formulas, showing each step on the board and catching the small slips that turn a right method into a wrong answer. CalculatorBin applies the same habits to everyday questions: how much concrete to order, what a loan really costs, how many days are left, or what grade you need on the final.

How I work on each calculator

• The method comes first. I write out the formula and work at least one example by hand before any code is written.
• Constants come from published sources. Bag yields from manufacturers’ data sheets, food-safety times from USDA, tax and retirement limits from the IRS, energy figures from the U.S. Energy Information Administration and the Department of Energy, and seed and fertilizer rates from university extension services. Each page lists its sources.
• Every answer shows its working. Results include the formula and, on most calculators, a “Show my working” list with your own numbers substituted — so you can check the arithmetic yourself.
• Tested before publishing. Each calculator is run against hand-checked answers and edge cases. There are currently 100 calculators on the site.

What I am not

I am a teacher, not a financial advisor, tax professional, lawyer, engineer or licensed contractor. The money, tax and building calculators here give planning estimates with every assumption visible; for decisions that matter, check with a qualified professional, your plan documents or your local building department.

Contact

If you find a mistake or want a calculator we don’t have yet, write to calculatorbin@gmail.com. I read every message and correct errors as soon as I confirm them. You can also read our editorial policy and how we build calculators.