Money · personal finance calculators

Money calculators

7 calculators for everyday money questions. Each works on your own figures, shows its formula and its working, and draws the result. None of them says what to do.

The calculators

Seven sums, each with its working shown.

Regular investingA fixed amount every month: what is paid in, and what an assumed rate adds.FV = P × ((1 + i)^n − 1) ÷ i
RetirementFrom monthly spending to the sum needed, and the saving that would build it.Spending then = S × (1 + π)^n
Loan EMIThe monthly payment on a loan, and how each one divides into interest and principal.M = L × i × (1 + i)^n ÷ ((1 + i)^n − 1)
InflationWhat a sum of money buys after years of rising prices.Cost then = A × (1 + π)^t
Goal plannerA target and a date: the monthly amount that would reach it.P = (T − L × (1 + i)^n) × i ÷ ((1 + i)^n − 1)
Tax dragThe same sum with no tax, tax each year and tax at the end, at your own rate.No tax: FV = A × (1 + r)^t
Rule of 72Years to double at a steady rate: the rule beside the exact figure.Rule of 72: years ≈ 72 ÷ r, with r as a percentage

How to read them

An assumed rate is not a forecast.

Every growth, inflation or tax rate on this page is an assumption that you enter. The figure a box opens with is an example to be replaced, not a suggestion. An assumed rate is not a forecast: real returns vary from year to year and can be negative, prices do not rise at a steady pace, and tax rules differ between countries and change.

Educational information, not investment advice or a recommendation to trade.

The rate is yours.
A calculator needs a rate of growth, of inflation or of tax, and nobody knows the first two in advance. Each box opens with an example figure so that the page has something to draw. It is there to be replaced.
The formula is on the page.
Each result is shown with its formula and with your own figures put into it, line by line, so that it can be checked by hand or in a spreadsheet.
No currency is assumed.
The arithmetic is the same in every currency. A symbol can be chosen for the figures, or left off.
Nothing is kept.
The sums are done in your browser. Nothing you type is sent anywhere or stored, and it is gone when the page is closed.

Trading foreign exchange on margin carries a high level of risk, and may not be suitable for all investors. The high degree of leverage can work against you as well as for you. Before deciding to trade foreign exchange you should carefully consider your investment objectives, level of experience, and risk appetite. The possibility exists that you could sustain a loss of some or all of your initial investment and therefore you should not invest money that you cannot afford to lose.