Compound interest is often called the eighth wonder of the world. Understand it, and you can grow wealth exponentially. Ignore it, and you might end up paying for it — literally.
How to benefit from compound interest is one of the fundamental things to get your head around when you start to get to grips with money. So grab a tea and let's get into it.
What is compound interest?
Compound interest is interest earned on interest.
I'll say that again so it sinks in.
Compound interest is interest earned on interest.
Unlike simple interest, which only grows your original deposit, compound interest reinvests what you earn — so your money grows faster over time.
Imagine you save £1,000 in a savings account earning 5% interest per year.
With simple interest, you take the £50 out at the end of each year. Your original £1,000 stays the same.
With compound interest, you leave the £50 in the account. Now your total is £1,050, and next year you earn 5% on that larger amount.
The more you have, the more it grows. The more it grows, the more you have.
Why compounding is a beautiful thing
The best way to explain it is to show it. Here's the same £1,000 at 5% interest, over time:
Over 3 years:
- Simple interest: £1,150
- Compound interest: £1,158
Not life-changing yet, right?
Over 30 years:
- Simple interest: £2,500
- Compound interest: £4,322 — nearly double
Over 50 years:
- Simple interest: £3,500
- Compound interest: £11,468
This is the magic of compounding. Even small amounts grow significantly given enough time. The work happens while you sleep — as long as you give it enough runway.
How to make compound interest work for you
Start today. Even if it's £10, £50, or £100 — you can't grow interest on nothing. Get something working for you now.
Be consistent. Small, regular contributions matter more than one-off deposits.
Reinvest your earnings. Leave your interest or dividends in the account rather than withdrawing them.
Use tax-efficient accounts. Maximise growth by saving in ISAs or pensions, where returns are protected from tax.
A real example: saving for your children
If you save £50 a month for a child from birth to 18, at an assumed 5.5% annual return, they'll have approximately £18,211 on their 18th birthday. That's from £10,800 of actual contributions — the rest is compounding doing the work.
Why it matters especially for women
Understanding compound interest can be transformative for women at any life stage. Whether you're saving for retirement, building a safety net, or funding your children's future, compounding turns small, consistent savings into significant wealth.
It's particularly important if you're taking a career break or working part-time — maximising contributions early can help offset gaps in earnings later. Starting five years earlier matters enormously. Starting today matters more than waiting until you have more to invest.
Nothing in this post is financial advice. For personalised guidance, speak to a regulated financial adviser.
Also on Femme Finance:
- How much could you save in a SIPP?
- The coffee habit compound interest experiment
- How to use the pensions dashboard
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