About Calculator Pro
Calculator Pro is a free collection of more than 400 online calculators and unit converters covering finance, health, mathematics, dates and construction. Every tool runs on a published formula, shown on this page, and returns a result without requiring an account, an email address or a download.
What this site is for
Most people arrive here with one number to work out: a monthly mortgage payment, a BMI, how many days until a date, how many inches are in 154 centimetres. The site exists to answer that one question quickly and then get out of the way.
There is no login requirement for any calculator. Accounts exist only so that you can save tools to a favourites list; the calculators themselves work identically whether you are signed in or not.
How the calculators are built
Each calculator implements a standard, published formula rather than an approximation or a lookup table. The four examples below are the exact expressions used in the site's source code, and they are representative of how the rest are written.
| Calculator | Formula used | Basis |
|---|---|---|
| BMI | BMI = weight (kg) ÷ height (m)² | Quetelet index. Categories are split at 18.5, 25.0 and 30.0, the standard WHO adult cut-offs. The healthy-weight range shown is 18.5–24.9 × height². |
| Mortgage payment | M = P · r(1+r)ⁿ ÷ ((1+r)ⁿ − 1) | Standard amortisation, where r is the monthly rate and n the number of payments. A full month-by-month amortisation schedule is generated, then property tax, insurance, PMI and HOA fees are added to give a PITI total. |
| Compound interest | FV = P(1+r)ⁿ + PMT · ((1+r)ⁿ − 1) ÷ r | Lump sum plus a regular-contribution series. Where an inflation rate is entered, the result is also deflated to present-day value. |
| Unit conversion | Exact defined factors | 1 inch = 2.54 cm and 1 lb = 0.45359237 kg are exact by international definition, not rounded constants. |
Accuracy, and where these tools stop being useful
A formula being correct is not the same as a result being right for you. Three limitations are worth stating plainly:
- Rates and rules change. Tax bands, contribution limits and lending rules are revised regularly. Where a calculator depends on one, treat the result as an estimate and confirm the current figure with the relevant authority.
- Population averages are not individuals. BMI, BMR and calorie estimates are derived from population studies. They do not account for muscle mass, body composition, pregnancy, or medical conditions, and they are not diagnostic.
- Rounding accumulates. Results are rounded for readability. Over a long amortisation schedule, a figure here may differ by small amounts from a lender's own statement, which may round at different points.
Reporting an error
If a result looks wrong, we would rather hear about it than not. Send the page address and the numbers you entered through the contact form and we will check the calculation against the source formula. Reports that identify a genuine error are acted on before new tools are added.
Who runs Calculator Pro
Calculator Pro is an independently operated website. It is not affiliated with, endorsed by, or connected to any bank, lender, insurer, health provider or government agency, and no third party pays for placement or for a calculator to produce a particular result.
The site is funded by advertising. Advertising has no influence on the formulas used or on the results any calculator returns.
Privacy and data
Calculator inputs are processed to produce your result, and some calculators include those values in the page address so the result can be bookmarked or shared. If you would rather a figure did not appear in a URL, avoid sharing that link. What is collected, why, and how to request its deletion is set out in the privacy policy.
Getting in touch
Corrections, suggestions and requests for a calculator that does not exist yet all go to the same place: the contact form. There is no separate support queue.
