Suppose your goal is $50,000 in 5 years, you already have $10,000 saved, and the account earns 4 percent a year. The tool first grows the existing $10,000 for 5 years, which becomes about $12,210 on its own. That leaves roughly $37,790 still to find from regular saving plus the interest those savings earn.
To fill that gap you need to put away about $570 a month. Over the 5 years your own money, the starting $10,000 plus the monthly deposits, totals about $44,200. Interest does the rest, adding around $5,800, and together they reach the $50,000 target. Saving earlier or at a higher rate shifts more of the burden onto interest and lowers the monthly amount, while a shorter timeframe raises it because compounding has less time to help.
Item
Amount
Savings goal
$50,000
Save per month
$570
Your total contribution (incl. starting $10,000)
$44,200
Interest adds
$5,800
How it is calculated
The calculator works in two steps. First it compounds your starting balance forward to the target date at the monthly equivalent of your interest rate, so it knows how much of the goal that lump sum will cover on its own. It subtracts that future value from the goal to find the shortfall still to be funded by regular saving. Then it uses the future-value-of-an-annuity formula in reverse to solve for the level monthly deposit that grows to exactly that shortfall over the number of months, with each deposit also earning interest. Your total contribution is the starting balance plus all the monthly deposits, and the interest figure is whatever is left of the goal once your own money is counted. The model assumes a steady rate and regular monthly deposits, so a variable savings rate would change the result.
Frequently asked questions
How much should I save each month?
It depends on your goal, your timeframe, and the return your savings earn. This tool solves for the monthly contribution that, combined with your starting balance and interest, reaches the target by your chosen date. Saving earlier means interest does more of the work, so the required monthly amount is lower.
Does KiwiSaver count toward a savings goal?
KiwiSaver funds are locked in until age 65 with two exceptions: a first-home withdrawal and serious financial hardship. IRD administers the scheme and employer contributions (minimum 3 percent of gross pay) plus the annual government contribution (up to $521.43 for the 2025/2026 year) add to your balance. If your goal is a house deposit, your KiwiSaver balance can form part of your target, but for general savings goals the funds are not freely accessible.
Is interest earned on savings taxable in New Zealand?
Yes. Interest earned on bank deposits is taxable income in New Zealand. Your bank deducts Resident Withholding Tax (RWT) at the rate you nominate, which for most individuals is 17.5 percent, 30 percent, or 33 percent depending on total income. The effective return on your savings is therefore the stated rate minus your RWT rate. If you nominate the wrong rate and underpay, IRD will assess the difference at tax time.
What savings rate should I use in the calculator?
New Zealand bank term deposit rates for 2025/2026 range roughly from 4 percent to 5.5 percent per year depending on term length and provider. Notice saver and online savings accounts typically pay 3 percent to 4.5 percent. Use the after-RWT rate for the most accurate result: multiply the advertised rate by (1 minus your RWT rate). For example, a 5 percent account with 17.5 percent RWT returns about 4.125 percent after tax.