Calculators
Everyday math โ percentages, BMI, loans and more.
About calculators
Calculators for the arithmetic that is easy to get wrong under time pressure: percentage change, a loan repayment, compound growth on savings, a tip split between an awkward number of people, BMI, or how many days there are until a deadline.
The financial calculators are the ones worth understanding rather than merely using. A loan or EMI calculation is not simply principal plus interest divided by months โ it uses an amortisation formula in which every payment is split between interest and principal, and the interest portion is largest at the beginning. This is why paying an extra amount early in a mortgage reduces the total cost far more than the same amount paid in the final years, and why the total interest figure is often startling the first time someone sees it written down.
Compound interest works in the same direction but in your favour, and rewards time more than it rewards contribution size. Regular monthly contributions started early beat larger contributions started late, frequently by a wide margin, because each year's growth compounds on every previous year's growth. The projection tool makes that concrete: change the start year rather than the amount and watch which one moves the final figure more.
One honest caveat on the health calculators. BMI is a population-level screening measure derived from height and weight alone. It does not distinguish muscle from fat, and it systematically misclassifies muscular people as overweight and some sedentary people as healthy. It is a starting point for a conversation with a doctor, not a diagnosis.
Frequently asked questions
How is a loan or EMI payment actually calculated?
Using the standard amortisation formula, where each payment covers the interest accrued that period plus a portion of the principal. Because interest is charged on the outstanding balance, early payments are mostly interest and later payments are mostly principal. That is why overpaying early saves disproportionately more than overpaying late.
Why does compound interest grow so much faster than expected?
Because each period's growth is calculated on the total including all previous growth, not just on your original deposit. The effect is modest over a few years and dramatic over a few decades, which is why the number of years invested usually matters more than the amount invested per month.
Is BMI a reliable measure of health?
Only loosely, and only at population scale. It uses height and weight alone and cannot distinguish muscle from fat, so athletes are routinely classified as overweight. Treat it as one rough indicator among several rather than a verdict, and discuss anything concerning with a doctor.
Can I rely on these for a real financial decision?
They use standard formulas and the arithmetic is correct, so they are reliable for comparing options and understanding the shape of a commitment. They do not account for fees, insurance, tax treatment, rate changes or early-repayment penalties, all of which vary by lender and country. Use them to inform a decision, then confirm the exact figures with the provider.