Money you borrow. The loan calculator handles any fixed-rate instalment debt — car finance, personal loans, EMI. The mortgage calculator does the same arithmetic but starts from a property price and deposit rather than a loan amount.
Money that grows. The interest calculator runs forwards: put this much in, see what it becomes. The savings goal calculator runs backwards: name the amount you need and it solves for the monthly deposit.
Money in the moment. Discount, tip and ROI are single-step calculations you do at a till, a restaurant table, or when judging whether something paid off.

What all of these leave out

Every finance tool on this site computes principal and interest only. That is deliberate — fees vary by lender, country and product, and a calculator that silently guessed at them would be worse than one that admits the gap. So the figures exclude arrangement and origination fees, broker commission, property tax, buildings and life insurance, early-repayment penalties, and any tax on interest or gains.

The practical consequence: treat these numbers as the floor, not the total. A mortgage payment from this site will be lower than the sum that actually leaves your account each month, and a savings projection ignores the tax you may owe on the growth. When you have a real offer in hand, the lender's own figures are the ones that count.

A note on currency

None of these tools assume a currency. Enter euros, pounds, dollars or rupees and the arithmetic is identical — interest rates and percentages are dimensionless. The only place it matters is tipping convention, which is cultural rather than mathematical, and the tip calculator page covers how expectations differ between countries.

Going deeper

Four of the guides deal with finance in more detail than a tool page allows: how loan interest is actually computed, where each mortgage payment goes, how much house you can afford, and why ROI needs annualising before you compare anything.