About CalcNest

CalcNest is a small collection of calculators for the questions people actually type into a search bar: what will this mortgage cost each month, how many calories do I need, what is 18% of this bill, how many business days until the deadline. Each one gives the answer instantly and then shows exactly how it got there.

Rachel Okafor, CPA

Rachel is a Certified Public Accountant in Columbus, Ohio, who taught algebra and statistics for nine years before moving into personal tax and small-business accounting. She writes and checks every formula on CalcNest.

Why it exists

In nine years of teaching algebra and statistics, the question I heard most was not “what's the answer?” but “why is that the answer?” Later, preparing returns and loan paperwork for clients, I saw the same thing from the other side: people trusted a number from an online tool without knowing what it assumed. A mortgage calculator that quietly ignores property tax, or a calorie estimate that never says which equation it used, is not much help.

So every CalcNest page follows the same rule: the result comes first, and right below it you'll find the formula, a worked example you can reproduce by hand, the assumptions, and the cases where the estimate is weak.

How the calculators are built and checked

Standard, published formulas. Loans use the ordinary amortization formula lenders use; health tools use named equations such as Mifflin-St Jeor (1990) and the U.S. Navy circumference method, with the source cited on the page.
Tested against known values. Every formula has automated tests that compare it with textbook results — for example, a $200,000 loan at 6% for 30 years must come out to $1,199.10 a month. The tests run before every release.
Calculated in your browser. Nothing you type is sent to a server. You can share a result because the inputs are placed in the page address, not stored by us.
No official data we can't cite. Calculators that need tax brackets, contribution limits or price indexes are only published with the official source and an “as of” date.

What CalcNest is not

These tools are for planning, learning and double-checking. They are not a loan offer, tax preparation or medical advice. If a decision is important, take the numbers to a lender, a tax professional or your doctor — they can see details a calculator can't.

Corrections

If you find a result that looks wrong, please tell us with the inputs you used (the “Copy link to this result” button captures them). Confirmed errors are fixed and the page's review date is updated.