Minimum Investment Efficiency Calculator NZ 2026/27
A platform that accepts a one dollar minimum is not the same as a platform where investing one dollar makes sense. The minimum is what they will let you put in; the efficient minimum is what the costs will tolerate, and where a fixed charge applies to every purchase those two numbers can be hundreds of dollars apart. The mechanism is simple and unforgiving: a fixed cost does not shrink with the investment, so the smaller the contribution the larger a share of it disappears before anything reaches the market. Three dollars sounds trivial and is thirteen percent of a twenty-five dollar contribution. This page measures that. It separates the fixed charge from the percentage ones, since they behave nothing alike as the amount changes, and reports what each investment actually costs as a proportion of itself. It then works backwards to the minimum size at which the total falls below whatever threshold you are willing to accept, and notes when a threshold is unreachable because the percentage component alone already exceeds it. The most useful output is the frequency comparison, because the amount is only half the question. The same money invested weekly, monthly or once a year attracts wildly different costs when each transaction carries a fixed charge, and batching contributions is usually a larger saving than any other change available to a small investor. Then set the fixed cost to zero and watch the whole problem disappear, which is the honest conclusion: where there is no fixed charge, frequency is free, minimums stop mattering, and small regular investing is exactly as efficient as large occasional investing.
Cost as a share = cost per transaction / the amount invested. This is the figure that decides whether an investment is worth making.
Minimum efficient size for a threshold = fixed charge / (threshold − percentage charge). Where the percentage charge is at or above the threshold, no amount is large enough and the calculator says so rather than returning a negative.
The frequency comparison holds the annual amount constant and varies how many transactions it is split into, so the only thing changing is the number of fixed charges paid.
Growth forgone on the costs compounds each transaction's cost at the expected return from the date it was charged to the end of the horizon, since a cost taken at the start of a contribution's life forgoes the longest run of growth.
Excluded: the cost of leaving money in cash while batching contributions, which offsets part of the saving; any minimum the provider imposes; tax; and any account or membership fee, which is charged per period rather than per transaction.
Not applicable to KiwiSaver, where contributions are not charged per transaction, so frequency costs nothing and no minimum efficient size exists.
All charges are user-entered. No platform is named, ranked or recommended, and the defaults are illustrative.
Not financial advice. Last verified: August 2026.
The minimum size for each cost threshold
| To keep total costs under | You need to invest | Cost at that size | How that compares to now |
|---|---|---|---|
| 5.00% | $66.67 | $3.33 | 1.3x your current amount |
| 2.00% | $200.00 | $4.00 | 4x your current amount |
| 1.00% | $600.00 | $6.00 | 12x your current amount |
| 0.75% | $1,200.00 | $9.00 | 24x your current amount |
| 0.60% | $3,000.00 | $18.00 | 60x your current amount |
| 0.50% | Unreachable | n/a | The percentage charge alone is 0.50% |
No investment is large enough to beat the percentage charge on its own. That is the floor, and only a platform with a lower percentage moves it.
The same money, invested more or less often
| Frequency | Each time | Transactions | Cost a year | Of what you invest |
|---|---|---|---|---|
| Weekly | $11.54 | 52 | $159.00 | 26.50% |
| Fortnightly | $23.08 | 26 | $81.00 | 13.50% |
| Monthly | $50.00 | 12 | $39.00 | 6.50% |
| Quarterly | $150.00 | 4 | $15.00 | 2.50% |
| Every six months | $300.00 | 2 | $9.00 | 1.50% |
| Once a year | $600.00 | 1 | $6.00 | 1.00% |
Identical money invested, $600.00 a year in every row. The only thing changing is how many fixed charges you pay.
What a platform with no fixed charge changes
| Frequency | With your fixed charge | As a share | With no fixed charge | As a share |
|---|---|---|---|---|
| Weekly | $159.00 | 26.50% | $3.00 | 0.50% |
| Fortnightly | $81.00 | 13.50% | $3.00 | 0.50% |
| Monthly | $39.00 | 6.50% | $3.00 | 0.50% |
| Quarterly | $15.00 | 2.50% | $3.00 | 0.50% |
| Every six months | $9.00 | 1.50% | $3.00 | 0.50% |
| Once a year | $6.00 | 1.00% | $3.00 | 0.50% |
The right-hand column does not move. With no fixed charge, frequency costs nothing and the question this page exists to answer stops existing.
A Minimum Is Not An Efficient Minimum
Most New Zealand platforms will now accept very small amounts. That says what they will process, not what makes sense.
On the worked example a $3.00 fixed charge plus 0.50% takes $3.25 from a $50.00 investment. That is 6.50% gone before anything is bought, and only $46.75 reaches the market.
A platform can happily accept a dollar and still charge a fee that makes investing a dollar absurd.
Worked Example: $50 A Month
Twelve investments a year totalling $600.00, costing $39.00.
To get the total cost under 1.00% you would need to invest $600.00 at a time, which is twelve times your current contribution.
Over ten years, $6,000.00 invested attracts $390.00 of costs. Had those costs been invested instead at 7.00%, they would have been worth $562.53 by the end.
The Floor You Cannot Beat
A fixed cost shrinks as a percentage when the investment grows, so any threshold above the percentage charge is reachable given a large enough contribution.
The percentage charge itself is different. On the worked example the total can never fall below 0.50%, whatever you invest, because that component scales with the amount rather than being diluted by it.
Only a platform with a lower percentage charge moves that floor. Our FX spread vs fee calculator is worth running on it, because a percentage conversion charge is frequently larger than advertised once the exchange rate mark-up is counted.
Batching Beats Everything Else Available
The frequency table is where the money is. Same $600.00 a year in every row.
Invested weekly it costs $159.00, which is 26.50% of everything contributed. Invested monthly, $39.00. Invested once a year, $6.00.
That is a factor of more than twenty-six between the top and bottom rows, from a decision that changes nothing about how much you save or what you buy.
It is not free. Batching leaves money in cash for longer before it starts working, and our cash drag calculator prices that side. On a small contribution facing a fixed charge, the fixed-cost saving usually wins comfortably.
Or Remove The Problem Entirely
Set the fixed charge to zero and the whole page collapses to a single number. Weekly, monthly, annually, every frequency costs 0.50%.
No minimum efficient size exists, batching gains nothing, and a small regular contribution is exactly as efficient as a large occasional one.
That is the honest conclusion of this calculation, and it is why the fixed charge is the first thing to check about a platform rather than the last. A low percentage charge with a fixed fee attached can be far worse for a small regular investor than a higher percentage with no fixed fee, and the crossover is exactly the arithmetic our fixed fee vs percentage fee calculator works through.
Why The Cost Compounds Worse Than It Looks
A transaction cost is charged at the very start of a contribution's life, which means it forgoes the longest possible run of growth.
On the worked example, $390.00 of costs across ten years would have been $562.53 had it stayed invested. The gap grows quickly at longer horizons, because the earliest costs have the most time to have compounded.
Our managed fund fee drag calculator makes the same point for annual fees, where the effect is larger again because the charge repeats every year.
This Does Not Apply To KiwiSaver
KiwiSaver contributions are not charged per transaction. Money arrives with each pay and no fixed fee is levied on it, so frequency costs nothing and no minimum efficient size exists.
The costs that matter there are the annual fund fee and any fixed membership charge, both of which are charged per period rather than per contribution. Our KiwiSaver fee calculator covers those.
Everything on this page applies to direct investing, where a brokerage or transaction charge lands on each purchase you make.
Related NZ Investing Cost Calculators
- Fixed Fee vs Percentage Fee Calculator: the same trade-off on annual fees.
- Managed Fund Fee Drag Calculator: what an annual fee costs over a lifetime.
- FX Spread vs Fee Calculator: whether the percentage charge is what it claims.
- Cash Drag Calculator: the cost of batching contributions.
- KiwiSaver Fee Calculator: where per-transaction costs do not apply.
Frequently asked questions
How small is too small to invest?
It depends entirely on the fixed cost per transaction. On the worked example a $3.00 brokerage charge plus 0.50% on a $50.00 investment costs $3.25, which is 6.50% of the contribution. To get the total cost under 1.00% you would need to invest $600.00 at a time. With no fixed cost at all, no amount is too small.
What is the minimum efficient investment size?
Divide the fixed cost by the difference between your cost threshold and the percentage charge. On the worked example, getting under 2.00% needs $200.00 per transaction, under 1.00% needs $600.00 and under 0.75% needs $1,200.00. Anything at or below the percentage charge itself, in this case 0.50%, is unreachable no matter how much you invest.
Is it better to invest monthly or less often?
With a fixed cost per transaction, less often is dramatically cheaper. On the worked example, $600.00 a year costs $159.00 invested weekly, $39.00 monthly and $6.00 in a single annual payment. That is the same money going in, with the cost varying by a factor of more than twenty-six purely from how many times it is split.
Does zero brokerage really change things?
Completely, and it is the single most important input on the page. With no fixed cost the total is just the percentage, so on the worked example investing monthly and investing annually both cost 0.50%. Frequency becomes free, minimum sizes stop mattering, and small regular investing becomes as efficient as large occasional investing.
Should I wait and save up before investing?
Only if the fixed cost is high relative to what you can invest. Batching contributions into fewer, larger transactions reduces cost but leaves the money in cash for longer, which has its own cost. Where the fixed charge is zero the trade-off disappears entirely and there is no reason to wait, which is why the fixed cost is worth checking before changing your habits.
How much do these costs add up to?
On the worked example, $390.00 over ten years on $6,000.00 invested, which is 6.50% of everything contributed. Had those costs been invested instead at a 7.00% return, they would have been worth $562.53 by the end. The reason it compounds is that the cost is taken at the start of each contribution's life, so it forgoes the longest possible run of growth.
What is the difference between a minimum investment and a minimum efficient investment?
A minimum investment is what a provider will let you put in, which on many New Zealand platforms is now a dollar or less. A minimum efficient investment is what makes sense given the costs, which is a different and usually larger number. A platform can accept $1.00 and still charge you a fixed fee that makes $1.00 an absurd amount to invest.
Does this apply to KiwiSaver?
Generally not, because KiwiSaver contributions are not charged per transaction. Employer and employee contributions flow in each pay without a fixed fee, so frequency costs nothing and there is no minimum efficient size. This calculation applies to direct investing where a brokerage or transaction charge is levied on each purchase.
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