About CalculatorPlus
CalculatorPlus is a free reference library of calculators, each one built around a stated, checkable formula — not a black box.
How These Are Built and Checked
Every calculator is written against a specific, published formula, and that formula is printed on the tool page so anyone can check it. Before a tool goes live it is tested against two or three known-correct results — either hand-worked or taken from an authoritative published source — and the worked example shown on the page is one of those verified cases, not an invented one.
When a result looks wrong to you, the working is right there to compare against. If it turns out we made a mistake, it gets fixed and dated.
How We Handle Rates That Change
Some calculations depend on a number set by an outside authority that changes over time — a sales-tax rate, a Treasury bond rate, a state fee schedule. For those tools we do three things: cite the actual issuing body, show the value and the date we last verified it, and pre-fill the number into an editable field so you can overwrite it in one step if it has since changed.
That means a stale default never silently produces a wrong answer — you can always see where the number came from and when we last checked it.
What These Tools Are Not
CalculatorPlus is an educational and estimation resource. The health, legal, financial and insurance calculators are here to help you understand a calculation and get a ballpark figure — they are not a substitute for a doctor, lawyer, accountant or licensed professional.
Each of those tools carries a plain disclaimer saying so, and cites the model or formula it is based on so you can take that to a professional and check it.
Reporting an Error
If a calculator gives you a result you believe is wrong, tell us through the contact page and include the numbers you entered. We take accuracy seriously — wrong math is worse than a missing tool — and corrections are made promptly and dated.
Frequently Asked Questions
Who is behind CalculatorPlus?
CalculatorPlus is an independent calculator library. It is not affiliated with any government agency, financial institution, or the brands whose methods some calculators reference.
How often are rate-dependent tools updated?
We review rate-dependent tools on a regular cycle and whenever the issuing authority publishes a change. Each such tool shows its own 'last verified' date, and the input is editable so you are never locked into a stale figure.
Looking for a different calculator?
CalculatorPlus has free tools across finance, construction, math, health and more — each one showing the formula and a worked example.