How much difference does compounding frequency make?

Less than most people expect. On £10,000 at 5% for ten years, monthly rather than annual compounding adds around £120. The rate, the time and your contributions matter enormously more than the frequency.

What is the rule of 72?

A quick mental estimate: divide 72 by the annual percentage rate to get the approximate years to double your money. At 6%, that is twelve years. It is accurate enough for rates between about 4% and 12%.

Does this account for inflation or tax?

No — it projects nominal growth. To estimate real purchasing power, subtract expected inflation from your rate before entering it. At 7% growth and 3% inflation, entering 4% gives a more honest picture.

CalculatorsWorks offline

Compound Interest Calculator

Project the growth of an investment or savings pot over time, with optional regular contributions and configurable compounding frequency, plus a year-by-year growth table.

Getting started

How to use the Compound Interest Calculator

1
Enter your starting amount, expected annual rate and the number of years.
2
Add a regular monthly contribution if you plan to keep saving.
3
Choose how often interest compounds, then read the projected balance and total interest earned.

Why it helps

What makes this tool worth using

Separates your contributions from the interest earned, which shows compounding's contribution honestly.
The yearly table makes the accelerating curve visible rather than abstract.
Regular contributions are modelled properly, not approximated.

In practice

Common ways people use it

Projecting a pension or long-term investment pot.
Comparing savings accounts with different rates and compounding frequencies.
Showing a child or student why starting early matters more than starting big.