Personal finance
Personal finance calculators
Simple and compound interest, rate conversion, annuities: the tools for working out what money really earns, or really costs, over time.
Which calculation you need
Start from the question, not the formula. To find out what a lump sum will grow to, use simple interest for horizons under a year and compound interest beyond that. If you pay in or receive a fixed amount at regular intervals, you are in annuity territory: future value when looking forward, present value when asking what it is worth today. The two equivalent-rate calculators come before all the others, because in every financial formula the rate and the period must share the same unit. The break-even and ROI calculators look at a business decision instead: the first tells you how much you have to sell to cover your costs, the second what the money you put in actually returned.
Simple interest
Capital, rate, duration or final amount when interest is not capitalised.
Equivalent simple rate
From annual to monthly and back, under simple interest.
Compound interest
Exponential growth of capital with periodic capitalisation.
Equivalent compound rate
Exponential rate conversion, the correct one when interest compounds.
Annuity future value
How much you accumulate paying in a constant instalment over time.
Annuity present value
What a stream of future receipts is worth today.
Break-even point
How many units you have to sell to cover fixed costs and start making a profit.
ROI
The percentage return on an investment, annualised as well.
Savings goal
How much to pay in each time to reach a target amount by a deadline.
Personal loan
Monthly payment, APR and total cost of a personal or car loan, with the repayment schedule.
Inflation and purchasing power
What money will be worth in the future, what a past sum is worth today, and the real return.
Bond yield
Gross and net yield to maturity, current yield and duration of a bond.
Regular investment plan
What a monthly investment in ETFs or funds grows to, after costs and tax.
Electricity usage and cost
How many kWh the appliances at home use and what they cost per day, month and year.