Retirement Calculator NZ Accuracy 2026: Are Free Tools Like Sorted Enough?

Free NZ retirement calculators give you a number in two minutes. But they bake in 2% inflation, a flat 2.5% post-65 return and a drawdown to zero at 90. Here is where they help, where they fall short, and when an independent adviser adds real value.

Type your age, income and KiwiSaver balance into Sorted's calculator and it hands you a number in about two minutes. It is a useful, free first step for any New Zealander planning their retirement.

But the accuracy of that number rests on a stack of fixed, regulator-set assumptions: 2% inflation, 3.5% pay rises, a flat 2.5% return after age 65, and your savings drawn down to zero by age 90 ⁶⁷. None of those will be exactly true for you. This guide shows what free calculators do brilliantly, where they quietly fall short, and the point at which a real plan is worth paying for.

TL;DR: Free NZ retirement calculators (Sorted, bank and provider tools) are a useful starting point, but they run on fixed FMA assumptions: a flat 2.5% return after 65 and drawdown to zero by age 90 ⁷. They cannot model your tax, decumulation order, sequence risk or behaviour. Use a calculator for the number; an adviser for the plan.

What do free NZ retirement calculators do well?

Quite a lot.

• They give you a target number fast. Sorted's KiwiSaver and retirement calculators (run by Te Ara Ahunga Ora, the Retirement Commission) let you see, in plain dollars, the weekly income your current savings path is likely to produce on top of NZ Super ⁶.
• Their assumptions are regulated, not marketing. The return figures inside KiwiSaver projections are fixed by the FMA — Defensive 1.5%, Conservative 2.5%, Balanced 3.5%, Growth 4.5%, Aggressive 5.5% after fees and 28% tax ⁷. Every provider tool, from Booster to BNZ to Fisher Funds, uses the same numbers, so you can compare apples with apples.
• They make the gap visible. NZ Super pays a single person living alone $555.15 a week after tax ⁸, against Massey's estimate that a single metro retiree spends $705 a week (no-frills) to $791 (choices) ⁹. Seeing that gap is a clear prompt to review your contribution rate.
• They are free, private and instant. No appointment, no email address, no sales pitch.

If you have never run the numbers, start with Sorted's free calculator. The useful question is not whether calculators help — they do — but where they stop. If you are already close to retirement and want the plan rather than the number, you can book a free review instead.

How accurate are retirement calculators — and where do they fall short?

A calculator is accurate given its assumptions: feed it fixed inputs and the maths is sound. But real retirement is decided by four things the tool cannot see, and that is where calculator accuracy quietly breaks down.

Tax: PIR, the contribution threshold and the new income cap

Most calculators assume a 28% PIR (prescribed investor rate) baked into the FMA returns ⁷. But your PIR might be 10.5% or 17.5% — the thresholds moved on 1 April 2025 to $15,600 / $53,500 / $78,100 ⁵, and an overpaid PIR is a common and fixable error.

Calculators also rarely flag that the full KiwiSaver government contribution still needs $1,042.86 of your own money between 1 July and 30 June ¹, that the match was halved in Budget 2025 to 25c per $1, capped at $260.72 a year ², and that members earning over $180,000 now get nothing ². A tool projects forward; it does not tell you that you are about to miss free money this year.

Sequence-of-returns risk

This is the flaw that does the most damage. Calculators assume a smooth, flat return — Sorted and the FMA use 2.5% a year after 65 ⁷; MoneyHub's drawdown modelling uses a flat 2.25% ¹¹. Markets do not move in straight lines. If a sharp downturn lands in the first few years of your retirement while you are drawing income, you sell more units at low prices and your money can run out years early — even if the long-run average matches the calculator exactly. No free tool models this.

Decumulation: the order you spend matters

Calculators model the saving years well and the spending years crudely — most just draw your balance down to zero over 25 years to age 90 ⁶. They cannot decide whether you should run down KiwiSaver first or last, when to switch some of a Growth fund to Conservative, or how to coordinate KiwiSaver with other savings, rental income or part-time work. The NZ Society of Actuaries frames the choice as a flat 6% drawdown rule versus a 4% inflation-adjusted rule ¹² — and a flat tool picks neither for you. Decumulation is where the real planning lives, and it is exactly where the tools go quiet.

Behaviour: the gap between the plan and what you actually do

The biggest variable in any projection is you. A calculator assumes you stay invested through every crash, never raid your KiwiSaver for the wrong reasons, and adjust your contributions on schedule. The 2022 and 2020 market falls showed how many people switch to Cash at the bottom and lock in the loss. Avoiding that single mistake can outweigh years of fees.

What assumptions are baked into Sorted and bank calculators?

This is the part most people never read. Under the bonnet, almost every NZ retirement tool runs on the same regulated engine. Here is what they assume.

The fund-return figures are identical across providers because the FMA fixes them: Defensive 1.5%, Conservative 2.5%, Balanced 3.5%, Growth 4.5%, Aggressive 5.5% ⁷. Westpac, Booster, BNZ and Fisher Funds all plug in the same numbers, with minor wording differences. So when two bank calculators give you different answers, it is almost always your inputs that differ, not the maths.

Two things to notice. First, 2.5% after 65 is conservative — it assumes you de-risk hard at retirement, which may not suit a 65-year-old with a 30-year horizon. Second, drawing to zero at exactly 90 is a planning convenience, not a strategy: roughly half of 65-year-olds will live past 90, and the tool has no answer for them.

When is a calculator enough, and when do you need advice?

Be honest about which camp you are in. A calculator is genuinely enough for plenty of people.

The pattern is simple. Far from retirement with a tidy situation, the calculator is enough — run it once a year. Close to retirement, or with more than one pot of money, the questions stop being "how much" and start being "in what order, in what fund, and what if markets fall in year two" — and those are advice questions. If that is you, book a free review.

How does an independent adviser differ from a provider's tool?

A bank or fund-manager calculator is built to project their scheme. It will never tell you that you are in the wrong fund, on the wrong PIR, or with the wrong provider — because the answer it is allowed to give is always "keep saving here."

An independent adviser holds no in-house product, so they can compare across Simplicity, Milford, Generate, Booster, Kernel, Fisher Funds and the bank schemes and recommend on fit, not on what they sell.

A common gap is the government contribution: a member can reach 30 June short of the $1,042.86 needed to collect the full match, because the calculator showed their balance at 65 but never flagged the deadline. That is the difference between a projection and a plan.

What do you get from a Smiths retirement review that a calculator can't give?

Three things a tool structurally cannot offer.

1. The right PIR and the full government match, locked in. An adviser checks your PIR against the $15,600 / $53,500 / $78,100 thresholds ⁵ and makes sure you clear the $1,042.86 contribution threshold before 30 June so you collect the full $260.72 ¹². A free tool assumes a 28% PIR and never checks the deadline.

2. A fund and a drawdown plan that match your actual horizon. Not a flat 2.5% to age 90 ⁷, but a strategy for which fund to hold approaching and through retirement, and the order to spend your pots to manage sequence risk — the decumulation question no calculator answers.

3. Someone to call when markets fall. An annual KiwiSaver review and an adviser on the phone help keep people invested through the bad years, which is where much of the long-run return comes from. That is the behaviour coaching, accountability and cross-provider fund comparison a free tool cannot give.

See how it works — a free, no-obligation 30-minute conversation with an adviser, not a sales call.

How to use a calculator before your review to save time

Do this first and your review goes twice as far:

1. Run Sorted or our retirement projection tool and note the weekly income figure it gives you.

2. Check it against your real spending. Compare it to Massey's guideline — single metro $705/wk (no-frills) to $791 (choices), couple metro $937/wk (no-frills) to $1,780 (choices) ⁹ — and against NZ Super of $555.15/week (single living alone) or $427.04/week each for a qualifying couple ⁸.

3. Write down your inputs: current balance, contribution rate, fund type and your PIR. If you do not know your PIR or fund, that alone is worth booking a review for.

4. Bring the number to your review. An adviser starts from your figure and pressure-tests the assumptions behind it.

Frequently asked questions

Are free retirement calculators accurate? They are accurate given their assumptions — but those are fixed: 2% inflation, a flat 2.5% return after 65, and savings drawn to zero by age 90 ⁶⁷. They are reliable for a rough target number and useless for predicting your exact balance, because real returns are volatile and your tax and spending are personal.

What return do Sorted and bank KiwiSaver calculators assume? The FMA fixes them after fees and 28% tax: Defensive 1.5%, Conservative 2.5%, Balanced 3.5%, Growth 4.5%, Aggressive 5.5% ⁷. From age 65 every tool assumes a flat 2.5% return ⁷. That is why two different bank calculators usually agree once your inputs match.

Does a calculator account for my PIR? Generally no — most bake in 28%. If your taxable income is $53,500 or less your PIR may be 17.5%, or 10.5% under $15,600 ⁵. An incorrect PIR is a common and fixable error, and a calculator will not catch it.

Will a calculator tell me if I am in the wrong KiwiSaver fund? No. It projects whatever fund you select; it will not say a Conservative fund is too cautious for a 35-year-old, or compare Simplicity against Milford or Generate. That comparison is what an independent review is for.

Is NZ Super enough on its own? For most people, no. NZ Super pays a single person living alone $555.15 a week after tax ⁸, while Massey estimates a single metro retiree spends $705 (no-frills) to $791 (choices) a week ⁹. The gap is exactly what your KiwiSaver and other savings need to fill — and the lump sums needed range from $46,000 to over $1,033,000 depending on household and lifestyle ¹⁰.

Do I still need advice if the calculator says I'm on track? If you are young with a simple, single-fund setup, probably not — just re-run it yearly. Within about ten years of retiring, or with more than one pot of money, the questions become drawdown order and sequence risk, which calculators cannot model.

General information, not personalised financial advice. Seek advice tailored to your situation before acting. Craig Smith Business Services Ltd (FSP712931), trading as Smiths Financial, holds a Class 2 licence issued by the Financial Markets Authority and is a member of the Financial Dispute Resolution Service (FDRS). Written by Henry Smith, Financial Adviser; reviewed by Craig Smith, Principal Adviser. Last reviewed 16 June 2026.