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Finance Calculator

Free Investment Calculator for New Zealanders

Long-run NZX share returns have averaged 7-9% annually before tax and fees. The calculator compounds a starting amount plus monthly contributions, so you can see how much of the final number is contribution and how much is growth.

Your investment

$10,000
$
$0$500k
$500
$
$0$5k
7.00%
%
0%15%
20 years
years
150
Future value
$300,540
at the end of the period

Starting with $10,000, contributing $500/month at 7.00% over 20 years.

Starting amount$10,000
Total contributions$120,000
Total contributed (incl. start)$130,000
Investment growth$170,540
Growth as % of total56.7%

About our Investment Calculator

$25,000 plus $500/month for 25 years at 7% reaches $539,591. Of that, only $175,000 is contributions; the remaining $364,591 is investment growth. Compounding does most of the work over 25-year horizons.

How to use it

Enter starting balance, monthly contribution, expected return, and the time horizon. The calculator returns the projected balance and a split between contributions and growth.

Why use it

For comparing investment scenarios head-to-head: different return assumptions, different contribution rates, different time horizons. Useful as a sanity-check on KiwiSaver and managed-fund projections.

The maths behind it

Formula: FV = P(1+r/12)12n + M × ((1+r/12)12n − 1) ÷ (r/12)

P is the starting investment. M is the monthly contribution. r is the annual return rate. n is the years. The first term grows the lump sum; the second is the future value of the contribution stream. Identical maths to the compound-interest calculator, framed for NZ-specific investment vehicles.

Worked example

Tobias, accountant in Cambridge, with $25,000 starting balance + $500/month for 25 years at 7%.

Tobias has $25,000 saved in an NZX-listed index fund. He adds $500 a month and assumes a 7% long-run return (between balanced and growth fund averages).

Over 25 years: starting $25,000 grows to $135,701. Monthly contributions of $500 ($150,000 total) compound to $403,890. Final balance: $539,591.

Of that $539,591, only $175,000 is contributions; the remaining $364,591 is investment growth. Compounding does most of the work over 25-year horizons.

Things to keep in mind

  • Returns are not guaranteed. The 7% default is a long-run average for NZX-listed equity funds. Actual annual returns vary; growth funds carry higher long-run averages with bigger swings.
  • Tax leakage. PIEPIRPrescribed Investor Rate; the PIE rate the investor selects based on their income.View in glossary → funds (including KiwiSaver and many NZ-listed funds) tax returns at the investor’s PIR (10.5%, 17.5%, or 28%). Direct holdings can incur RWTRWTResident Withholding Tax; tax taken at source from NZ-resident interest and dividends.View in glossary → on dividends and capital-gains tax through FIFFIFForeign Investment Fund; non-NZ shares and certain offshore holdings taxed under special rules.View in glossary → on offshore investments.
  • Fees compound against you. Annual fund fees of 1% reduce a 25-year final balance by roughly 20% relative to a no-fee scenario. Subtract your fund’s fee from the input return for a more honest projection.
  • Inflation matters. A 7% nominal return at 2.5% inflation is a 4.4% real return. The calculator works in nominal dollars; subtract inflation for a real-purchasing-power view.

NZ-specific notes

FMA
NZ KiwiSaver and managed-fund returns. The Financial Markets Authority publishes audited five- and ten-year returns by fund category. NZX-listed equity funds typically average 7-9% before fees over long horizons.
Source
IRD
PIR rates on PIE income. 10.5%, 17.5%, or 28%, capped so investors are not taxed worse in a PIE than outside one. Most NZ retail investment funds are PIEs.
Source
NZX
NZ share market. The NZX 50 Index tracks the 50 largest NZX-listed companies. Long-run total returns including dividends have averaged around 8% over rolling 20-year periods.
Source
Sorted
Investor education. Te Ara Ahunga Ora Retirement Commission’s Sorted website covers NZ investment options, fund types, and tax treatment in plain English.
Source

FAQs

What return rate should I use?

Long-run NZ balanced fund returns average 6-7% before fees; growth funds 7-9%; conservative 3-5%. Subtract about 1% for fees and any tax leakage to get a net figure.

How does this differ from the compound interest calculator?

Same maths. This page is framed around investment vehicles (KiwiSaver, NZX funds, term deposits) and the related tax considerations; the compound interest calculator is the generic version.

Do I pay tax on the growth?

PIE funds tax growth at your PIR. Direct shares pay RWT on dividends. Capital gains on most NZ shares are not taxed (unless held under a "trader" intent). FIF rules apply to most offshore holdings above $50,000.

Can I withdraw the money anytime?

Most NZ retail managed funds allow withdrawal within 5-10 business days. KiwiSaver is locked until 65 (with first-home and hardship exceptions). Term deposits are locked for the contracted period.

References & sources

  1. Financial Markets Authority, "KiwiSaver annual report (audited returns)". fma.govt.nz
  2. Inland Revenue, "Portfolio Investment Entities (PIE)". ird.govt.nz
  3. NZX, "NZ share market". nzx.com
  4. Te Ara Ahunga Ora Retirement Commission, "Sorted investing guides". sorted.org.nz

Last reviewed

✓
Reviewed 6 May 2026, current to NZ retail investment market in mid-2026

Share your numbers

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Disclaimer: This calculator is for information only and is not financial advice. Real investment returns vary; past performance does not predict future returns. Calculator.org.nz is not a registered Financial Advice Provider. For tailored investment advice, talk to a licensed financial adviser.