Retirement Number Calculator

How this calculator works

The maths behind a retirement number is simple once you break it into two steps. First, work out how much of your target income NZ Superannuation already covers. NZ Super is paid from age 65 to almost all New Zealand residents who meet the residency rules, at a rate that depends on your living situation, and it is not means tested, so it is added on top of whatever your own savings provide rather than being reduced by them. Subtracting the NZ Super figure for your situation from your target annual income leaves the shortfall your own savings need to fund. Second, divide that shortfall by your chosen safe withdrawal rate. A withdrawal rate is simply the percentage of a portfolio drawn down each year, and dividing by a percentage is mathematically the same as multiplying by its reciprocal, so a 4% withdrawal rate means you need 25 times your annual shortfall (1 divided by 0.04), a 5% rate means 20 times, and a 3% rate means roughly 33 times. That reciprocal relationship is why the withdrawal rate you choose has such an outsized effect on the final number, and why the calculator shows your figure at 3%, 4% and 5% side by side rather than just one single answer.

What is a safe withdrawal rate

A safe withdrawal rate is the annual percentage of an investment portfolio that history suggests can be drawn down, adjusted for inflation each year, without a high risk of running out of money over a typical retirement length. The most widely cited figure, 4%, comes from research by American financial planner William Bengen in 1994, later reinforced by the 1998 Trinity study, both of which tested withdrawal rates against historical market returns over 30-year retirements. It is a useful rule of thumb, not a New Zealand government figure and not a guarantee. The rate that actually proves sustainable for any individual depends on how their money is invested, the sequence of returns they experience (a market fall in the first few years of retirement is far more damaging than the same fall later on), fees, tax, and how long their retirement turns out to last. Because of this, many planners now discuss a range of roughly 3% to 5% rather than a single fixed number, with more conservative retirees or those expecting a longer retirement leaning towards the lower end, and this calculator lets you test anywhere in that range, or beyond it, to see the effect.

Worked example

Say you would like $65,000 a year to live on in retirement, in today's dollars. You expect to retire at 65 and qualify for NZ Super as a single person living alone, currently $28,867.80 a year after tax on the standard M tax code. That leaves $65,000 minus $28,867.80, which is $36,132.20 a year that your own savings need to produce. At a 4% withdrawal rate, the nest egg required is $36,132.20 divided by 0.04, which comes to $903,305. If you wanted to be more cautious and used a 3% withdrawal rate instead, the same $36,132.20 shortfall would require $1,204,406.67, roughly $301,000 more. If you were comfortable with a more confident 5% rate, you would only need $722,644, around $180,000 less than the 4% figure. The size of that swing, from about $722,000 to about $1.2 million on exactly the same income target, shows why the withdrawal rate you choose matters as much as the income figure itself.

A couple where both partners qualify for NZ Super, targeting a combined $80,000 a year, would net off the combined couple rate of $44,412.16 a year, leaving a shortfall of $35,587.84. At a 4% withdrawal rate that is a required nest egg of $889,696, a very similar figure to the single example above despite a higher combined income target, because two NZ Super payments are covering a larger share of the goal.

Why the withdrawal rate matters so much

Because dividing by a percentage is the same as multiplying by its reciprocal, small changes to the withdrawal rate move the final number by a large amount. Moving from 4% to 3% does not add 1 percentage point of extra saving, it multiplies the required nest egg by roughly 1.33. Moving from 4% to 5% divides it by 1.25. On a typical six-figure annual shortfall, that difference is easily hundreds of thousands of dollars. This is exactly why the results panel above shows your number at three different rates rather than a single figure: it is far more useful to see the range your true number probably sits within than to anchor on one withdrawal rate as if it were certain.

What this calculator assumes

• All figures are in today's dollars. If retirement is many years away, the actual dollar balance you accumulate by then needs to be larger again once inflation between now and retirement is added on top.
• NZ Super figures are the current net, after-tax rates on the standard M tax code, from 1 April 2026, for the living situation you select. NZ Super is reviewed and can change every April.
• The nest egg figure is a static target, not a year-by-year projection. It does not model market volatility, the order in which good and bad investment years occur (sequence-of-return risk), ongoing fund fees, or a fixed number of years the money must last.
• Results are shown before tax. Investment income drawn from your savings in retirement may be taxed, for example at your prescribed investor rate inside a KiwiSaver or other PIE fund, so you may need to draw a little more than the figures shown to end up with your target income in hand.
• The safe withdrawal rate is a planning rule of thumb from international retirement research, not a New Zealand-specific or guaranteed figure. Treat the range shown as indicative, not as a promise your savings will never run out.

Who this calculator is for

This is for anyone who wants a real dollar target for retirement instead of a vague sense that they should "save more". It suits people early in their working life who want a long-range savings goal, people within 10 to 15 years of retirement checking whether their KiwiSaver and other savings are tracking towards a realistic figure, and anyone comparing what a more modest versus more generous retirement income would actually cost to fund. If you already have a savings balance and want to know how long it would last at a given drawdown, rather than what balance you should be aiming for, our Retirement: How Long Will My Money Last Calculator answers that companion question directly.

Frequently Asked Questions about your retirement number

What is my retirement number?

Your retirement number is the nest egg you need saved to fund the gap between your target annual retirement income and NZ Superannuation, drawn down at a safe withdrawal rate. It is calculated as (target annual income minus NZ Super) divided by your chosen withdrawal rate.

What is a safe withdrawal rate?

The percentage of a retirement portfolio you draw down each year with a reasonable expectation the money lasts through retirement. The commonly cited figure is 4%, from research by William Bengen and the later Trinity study, though many planners now discuss a range of roughly 3% to 5%. It is a rule of thumb, not a guarantee.

Does this calculator include NZ Super?

Yes. Choose your living situation and the current NZ Super rate for that situation is netted off your target income before the calculator works out how much you need from savings. Select None to see the full number excluding NZ Super, useful if you plan to retire before age 65.

Why does the withdrawal rate change the answer so much?

The withdrawal rate is the divisor in the calculation. At 4% you need 25 times your annual shortfall; at 3%, roughly 33 times; at 5%, only 20 times. Small changes to this one assumption move the answer by hundreds of thousands of dollars on a typical shortfall.

Is this the same as how long my money will last?

No. This calculator sizes a target nest egg for a chosen ongoing withdrawal rate. Our Retirement: How Long Will My Money Last Calculator starts from an actual pot and drawdown amount and estimates how many years it lasts at an expected return, useful once you already have a balance.

Should I use today's dollars or future dollars?

This calculator works in today's dollars throughout. If retirement is many years away, remember the actual balance you accumulate by then needs to be larger again once inflation between now and retirement is added, since a dollar in 20 years buys less than a dollar today.

Does the nest egg figure include tax?

No, it is a pre-tax planning estimate. Investment income you draw in retirement may be taxed, for example at your prescribed investor rate inside a PIE fund, which can mean you need to draw slightly more than your target take-home figure.

What if I plan to retire before I qualify for NZ Super?

Select None for your NZ Super situation so the full target income is funded from savings alone. You may want to run the calculation twice, once for the years before 65 with NZ Super set to None, and again for the years after 65 with NZ Super included, since your required income from savings usually drops once NZ Super starts.

Related calculators

• KiwiSaver Retirement Projection Calculator: project your current balance and contributions forward to see how close you get to your number.
• Retirement: How Long Will My Money Last Calculator: starting from an actual pot, see how many years it lasts at a chosen drawdown.
• NZ Super Rate Calculator: check the current fortnightly, weekly and annual NZ Super rate for your living situation.
• NZ Super plus KiwiSaver Combined Income: see your total likely retirement income from both sources together.
• Retirement Calculator: full retirement savings projection and planning tool.

Official NZ sources

This calculator is built from primary New Zealand sources. Always confirm current figures against the official source for your situation:

• Work and Income: NZ Superannuation, eligibility and current payment rates
• Sorted (Te Ara Ahunga Ora, Retirement Commission): retirement planning tools and guidance
• Inland Revenue (IRD): KiwiSaver and prescribed investor rates