Compound interest: why your KiwiSaver grows faster than you think

Compound interest is when you earn returns not just on your original money, but on the returns that money has already earned. Over time this creates a snowball effect - your savings grow faster and faster because you're earning on a bigger and bigger amount.

A simple example

Say you make a one-off investment of $1,000 earning 10% a year.

Each year the dollar amount you earn gets bigger, even though the rate never changes. Keep that going and after 40 years your $1,000 becomes about $45,259 - without you adding another cent. (This is an illustration at a constant 10% - real KiwiSaver returns vary year to year - but the compounding principle is exactly the same.)

Einstein reputedly called compound interest the eighth wonder of the world: those who understand it, earn it; those who don't, pay it.

Why this matters for your KiwiSaver

KiwiSaver is a long-term investment, which puts compounding firmly on your side - the earlier you start contributing and the better your returns, the more powerfully it works. Three practical consequences:

Time beats timing. Money invested in your twenties has decades more compounding runway than money invested in your forties. This is why starting early - even starting your kids early - matters so much.

Small return differences become huge. A fund earning even 1% more per year, compounded over 30-plus years, can mean tens of thousands of dollars of difference. That's why your fund type matters more than most people realise.

Contributions early in life punch above their weight. Every dollar in early gets the longest ride. Want to see your own numbers? Run your projection in the KiwiSaver calculator.

Frequently asked questions

Does KiwiSaver actually pay "interest"?

Not in the bank-account sense - your KiwiSaver is invested in funds that earn returns from shares, bonds and other assets. But those returns compound in exactly the same way: gains are reinvested and generate their own gains over time.

How do I make compounding work harder for me?

Start early, contribute consistently, make sure you're in a fund type matched to your timeframe, and check your provider's long-term net returns (after fees). A free advice session can cover all four in half an hour.