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CalculatorNest is an independent project offering calculation tools and explanations in English and Arabic. Each calculator states its formula and assumptions and separates the mathematical result from its interpretation. Linking a source does not mean its publisher has reviewed this website or endorsed its results.
Where the methods come from
- Body mass index: weight in kilograms divided by height in meters squared. The calculator uses the adult categories for ages 20 and older described by CDC: adult BMI categories and calculation. BMI is a screening measure, not a diagnosis or a direct body-fat measurement.
- Calories: estimated resting energy uses the simplified equation published in Mifflin et al. (1990): original resting-energy equation, PubMed. The website then multiplies this by your selected activity factor. Those factors are additional estimates used by the tool, not part of the original resting-energy equation; actual needs can differ.
- Body fat: the calculator displays the circumference equations commonly called the U.S. Navy method and converts centimeters to inches before calculation. Potter et al. (2022): limitations of circumference estimates compared with DXA provides context on the limitations of these estimates and differences from device measurements. The result here is neither a medical assessment nor a military eligibility test.
- Loans and mortgages: the website models fixed monthly payments on a declining balance at a fixed nominal rate. CFPB: how amortization divides payments between principal and interest explains how repayments are divided. The formula and excluded costs appear on each tool's page; the tools do not calculate a fee-inclusive annual percentage rate (APR).
- Compound interest and savings: results depend on the amount, duration, rate, and compounding frequency. Investor.gov: compound-interest calculator inputs explains those inputs. This website's savings calculator assumes contributions at each month's end and excludes fees, tax, and inflation.
Percentage, discount, margin, break-even, and math tools use the arithmetic relationships shown beside their results. Tax and return rates are assumptions you supply. The website does not retrieve live tax rates or lending prices or check whether they apply in your country.
Examples you can reproduce
- In the percentage calculator, 15% of 250 is 37.5: multiply 250 by 15, then divide by 100.
- In the loan calculator, a 12,000 loan at zero interest over one year produces 12 monthly payments of 1,000, before any costs outside the calculator.
- In the BMI calculator, 81 kg and 180 cm produce 81 ÷ 1.8² = 25. This is the start of the adult overweight category; the number alone does not establish a person's health.
What the checks cover
The project includes automated tests for known results, zero interest, input boundaries, unit conversions, leap dates, and consistency between total principal repaid and the original loan. Other checks cover local saving, exports, and equivalent behavior in both languages. These checks help identify implementation errors; they cannot establish correctness for every possible case or suitability for every person.
This version has not received an independent external medical or financial review. Explanations and examples are educational. The website does not provide a diagnosis, diet prescription, financing offer, or investment recommendation.
Units, rounding, and comparisons
Read the unit beside each field. Enter 6 when you mean 6%, and use the same currency throughout a financial calculation. The website does not convert currencies. Default numbers are editable examples, not current prices or recommended rates.
Calculations use the numeric precision available in the browser before results are rounded for display. Adding displayed schedule figures can differ slightly from totals calculated before rounding. BMI categories use the unrounded value, so a value very close to a boundary can display as that boundary after rounding. For useful comparisons, change one assumption at a time and calculate again.
Your data and reporting errors
Calculations run in your browser. When you choose to save a calculation, its inputs stay on the same device and do not sync with a user account. Exported files can contain your inputs; see the privacy policy for details.
If you find an unexplained difference, note the calculator name, inputs and units, displayed result, and expected calculation or reference. The contact page explains the feedback options available for this version. Avoid including account numbers, medical records, or sensitive personal information. Loading a saved scenario calculates it again with the current tool; export a dated copy if you need to retain an earlier result.