Interest calculator
See how much a principal amount earns (or costs) over time, comparing simple interest against compound interest, in the currency you choose.
Fill in the fields and press Calculate to see your result here.
How this calculation works
Simple interest is P × r × t, calculated once on the original principal. Compound interest uses A = P × (1 + r/n)^(n×t), where n is how many times per year interest is added — each round of interest then earns interest itself, which is why compound growth accelerates over longer periods. The currency picker only changes the symbol shown — it does not convert your numbers.
Tips
More frequent compounding means slightly more growth
Monthly compounding earns a little more than annual compounding at the same stated rate, and daily a little more again — though the difference shrinks the more often it compounds.
The Rule of 72
Divide 72 by the annual rate to estimate how many years it takes money to double with compounding. At 6% that is about 12 years.
Time beats size
Because interest earns interest, leaving money invested longer usually matters more than the size of any single deposit.
Results are before tax and inflation
Interest may be taxed, and rising prices reduce what the money can buy, so the balance shown is a nominal figure.
Frequently asked questions
Which does a savings account use?
Most savings accounts use compound interest, typically compounded daily or monthly, even if interest is paid out monthly.
Which does a simple loan use?
Some short-term loans use simple interest, but many loans (including mortgages) are amortising loans — a different calculation covered by the mortgage and loan calculators.
Is this financial advice?
No, it's for general information only. Speak with a financial advisor for guidance on savings or investment decisions.