US Share FX Cost Calculator

For a New Zealand investor buying US shares, the foreign exchange fee is usually the largest single cost of the transaction and the one least likely to be compared. Platforms advertise zero brokerage prominently and disclose the FX rate in a fee schedule several clicks away, which means investors routinely choose a platform on a cost that is nil and ignore one that is one and a half percent. This page takes the fee rate as an input rather than assuming a provider, so it works for any platform, and it reports the cost three separate ways because each answers a different question. In New Zealand dollars, which is what left your account. In US dollars, which is the purchasing power you did not get. And as the percentage gain you now need simply to return to your starting position, which is higher than the fee itself because the gain has to be earned on the smaller amount that survived the conversion. It also shows the same conversion at three different fee rates side by side, since the practical decision is rarely whether to pay an FX fee at all but which rate to pay it at, and the difference on a typical purchase is larger than most people expect.

Calculate.co.nz is proud to be partnered with realtor.co.nz, a trusted resource for navigating the New Zealand property market. Their Helpful Articles section offers clear, well-structured insights across buying, selling, and building, making complex real estate topics more accessible. With a focus on up-to-date guidance and practical knowledge, they empower Kiwis to move forward with clarity and confidence in a constantly evolving property landscape.

Zero Brokerage Is Not Zero Cost

The single most expensive habit among New Zealand investors buying US shares is comparing platforms on brokerage. Brokerage is prominent, easy to understand, and increasingly zero. The FX fee is none of those things, and on a typical purchase it is the entire cost.

On the worked example, brokerage is $0.00 and the conversion costs $150.00. A platform advertising free trading has charged one and a half percent of your capital before a single share was bought.

Worked Example: $10,000 Becomes US$5,762.25

You convert $10,000.00 at a spot rate of 0.5850. With no fee at all you would receive US$5,850.00.

The platform charges 1.50%, which is $150.00, so only $9,850.00 is converted. At the same spot rate that produces US$5,762.25.

The difference is US$87.75 of purchasing power that never reached your account. In percentage terms it is 1.50% of what you started with, and you need a 1.52% gain to recover it.

Why The Break-Even Gain Is Higher Than The Fee

This trips people up and the arithmetic is worth seeing. A 1.50% fee does not need a 1.50% gain to recover, because the gain is earned on what is left rather than on what you started with.

You began with the equivalent of US$5,850.00 and now hold US$5,762.25. To get back to US$5,850.00 from US$5,762.25 requires a gain of 87.75 divided by 5,762.25, which is 1.52%.

The effect compounds as fees rise. A 3% fee needs 3.09%. A 5% fee needs 5.26%. It is a small distinction on a single trade and a meaningful one for an investor converting regularly.

The Rate Difference Is The Whole Decision

Almost nobody chooses whether to pay an FX fee. Everybody chooses which rate to pay it at, and the choice is usually made once, when opening an account, and then repeated on every conversion for years.

On $10,000.00, moving from 1.50% to 0.40% saves $110.00 on a single conversion. For an investor putting in the same amount monthly, that is $1,320.00 a year on money that has not been invested yet, every year, compounding into the returns never earned on it.

The rates commonly seen in the New Zealand market span roughly 0.3% to 1.5%. That range is wider, in cost terms, than the difference between most index funds' management fees, and it applies to money going in rather than to money already working.

Remember The Way Back Out

The fee is charged in both directions. Converting $10,000.00 in and the equivalent back out at the same rate costs $297.75, or 2.98% of the original amount, and requires a 3.07% gain to cover.

That has two practical consequences. It raises the return threshold at which the investment was worth making at all, and it argues strongly against trading US positions frequently, because each round trip pays the toll twice. Investors intending to hold for a decade can reasonably treat the entry cost as a one-off. Investors expecting to move in and out cannot.

Watch For The Cost That Is Not A Fee

A platform charging no explicit FX fee has not necessarily given you a free conversion. It may simply be quoting a rate below the mid-market rate and keeping the difference, which never appears in a fee schedule and is invisible unless you check the spot rate at the moment of conversion.

The test takes thirty seconds: note the rate you were given, look up the mid-market rate for the same moment, and calculate the gap as a percentage. Our FX spread versus fee calculator does the conversion so a marked-up rate can be compared like for like against an explicit fee.

Where This Sits In The Total Cost

The FX fee is the first of five costs a New Zealand investor pays on a US ETF. The others are brokerage, the fund's own expense ratio, US withholding tax on dividends, and FIF tax if your offshore holdings exceed the de minimis threshold.

Our total cost of owning a US ETF calculator combines all five into a single annual figure, our US withholding tax calculator handles the dividend side, and our FIF de minimis calculator tells you whether the FIF rules apply to you at all.

Related NZ Offshore Investing Calculators

• FX Fee Tier Break-Even Calculator: when a paid membership with a lower FX rate pays for itself.
• FX Spread vs Fee Calculator: what a marked-up rate costs compared with an explicit fee.
• Total Cost of Owning a US ETF: all five cost layers combined.
• US Withholding Tax on Dividends: what the W-8BEN is worth.
• Repatriation Cost Calculator: the full round trip, there and back.