Currency Risk in Overseas Shares: Calculate Your Return in Pounds

Currency Risk in Overseas Shares: Calculate Your Return in Pounds

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Evergreen trading tutorial: This guide uses hypothetical prices to explain foreign-exchange effects on overseas investments. It is educational information, not personalised advice, a currency forecast or a recommendation to hedge.

A UK investor can choose the right US share and still receive a very different return in pounds from the return shown in dollars. The share price moves in its local market, while the exchange rate changes how many pounds each dollar is worth.

Currency can amplify a gain, reduce it, turn it into a loss or soften a local-market decline. The relevant performance measure is therefore the return in the investor's home currency after conversion and costs.

Learning objective

By the end of this guide, you should be able to:

• separate local-asset return from currency return;
• calculate a GBP return from a US-dollar investment;
• understand why returns combine multiplicatively rather than by simple addition;
• distinguish hedged from unhedged exposure; and
• include currency, dividends and conversion costs in risk planning.

Two sources of return

For a UK investor holding a US share, the sterling result has two moving parts:

1. the share's return in US dollars; and
2. the dollar's return against sterling.

Express the currency component as pounds per dollar. The combined return is:

GBP return = (1 + USD asset return) × (1 + USD currency return in GBP terms) − 1

The multiplication matters because the exchange rate applies to the final dollar value, not just the original investment.

If a platform quotes GBP/USD as dollars per pound, a falling GBP/USD rate means one dollar buys more pounds. That normally helps the sterling value of an unhedged dollar asset. A rising GBP/USD rate means sterling strengthened, which normally reduces the sterling return.

Worked example: weaker pound amplifies a US-share gain

Assume a fictional US share rises from $100 to $110, a 10% local return.

At purchase, GBP/USD is 1.25 dollars per pound. The £ value of one $100 share is:

$100 ÷ 1.25 = £80.00

At sale, GBP/USD has fallen to 1.20. The £ value of the $110 proceeds is:

$110 ÷ 1.20 = £91.67

The sterling return is:

£91.67 ÷ £80.00 − 1 = 14.58%

The dollar strengthened against sterling. Measured as pounds per dollar, the currency return is:

(1 ÷ 1.20) ÷ (1 ÷ 1.25) − 1 = 4.17%

Combining the components:

(1 + 10%) × (1 + 4.17%) − 1 = 14.58%

Simply adding 10% and 4.17% gives 14.17%, which misses the interaction term.

Worked alternative: stronger pound absorbs most of the gain

Keep the same share move from $100 to $110, but assume GBP/USD rises from 1.25 to 1.35. The sale proceeds become:

$110 ÷ 1.35 = £81.48

Compared with the initial £80, the sterling return is only:

£81.48 ÷ £80.00 − 1 = 1.85%

The share gained 10% in dollars, but the stronger pound absorbed most of that gain. Neither scenario says what currencies will do next; both show why local price return is incomplete for an overseas investor.

The same effect applies to losses

If a US share falls 10% while the dollar rises strongly against sterling, the currency gain can reduce the loss in pounds. If the share falls and the dollar also weakens, the two effects compound.

This makes overseas exposure a combination of asset risk and FX risk. The currency position may diversify the portfolio in one period and increase drawdown in another.

Dividends and income

Overseas dividends are declared in the asset's currency and converted when received or withdrawn. The sterling income therefore depends on:

• dividend per share;
• withholding tax where applicable;
• the conversion exchange rate;
• broker FX spread or fee; and
• any account-level tax treatment.

A stable dollar dividend does not guarantee stable sterling income. Tax rules depend on the investor and account, so use current official guidance or qualified advice for personal decisions.

Hedged and unhedged funds

An unhedged overseas fund normally leaves the underlying currency exposure in place. A GBP-hedged share class uses derivatives—often forward contracts—to offset much of the currency movement.

Hedging is not free or exact. Results can differ because of:

• forward-rate differentials between currencies;
• transaction and management costs;
• hedge rebalancing frequency;
• imperfect hedge ratios;
• cash flows and market moves between rebalances; and
• the fund's chosen base and hedge currencies.

A hedged fund aims to reduce FX variation, not remove the underlying asset's market risk. It can outperform an unhedged version when sterling strengthens and underperform when sterling weakens.

Trading currency versus listing currency

A London-listed ETF priced in pounds can still hold US-dollar assets and carry dollar exposure. The screen currency shows how units trade; it does not by itself reveal the economic currency risk.

Likewise, an international company may earn revenue in several currencies even when its shares trade in London. Distinguish:

• trading currency;
• fund or company reporting currency;
• currencies of underlying assets, revenues and costs; and
• whether a hedge is actually applied.

Step-by-step FX-aware return process

1. Choose the home currency

For this guide it is GBP. All performance and risk should ultimately be translated into the currency used to fund goals and measure the account.

2. Record local asset values

Use purchase and sale prices, distributions and the number of shares. Apply any corporate actions consistently.

3. Record matching FX rates

Use rates corresponding to the actual cash flows and a consistent quote convention. Write whether the rate is GBP/USD or USD/GBP to prevent inversion errors.

4. Convert each cash flow

Translate purchases, dividends, fees and sales at their relevant rates. One end-of-period conversion is insufficient when money moved at different times.

5. Include conversion costs

Broker spreads, fixed charges and card or bank fees can materially affect frequent small trades. Use executable rates rather than an ideal mid-market rate.

6. Stress both components

Model the asset rising or falling alongside sterling strengthening or weakening. Do not assume currency will always offset the asset.

7. Size total exposure

Several US holdings may create one large dollar position. Combine them before deciding the portfolio is diversified. Our correlation and concentration guide explains this portfolio view.

Hypothetical four-scenario grid

For a simple one-period illustration:

Local asset return	Dollar return vs GBP	Approximate combined GBP return
+10%	+5%	+15.5%
+10%	−5%	+4.5%
−10%	+5%	−5.5%
−10%	−5%	−14.5%

The calculation uses multiplication. These are scenarios, not forecasts, and exclude fees, tax and tracking differences.

Common mistakes

1. Reporting only the local share return. The investor spends and measures wealth in the home currency.
2. Reading GBP/USD backwards. A higher rate means more dollars per pound, not a stronger dollar.
3. Adding asset and FX percentages. Compounding creates an interaction term.
4. Assuming a GBP listing removes dollar risk. Trading currency and economic exposure differ.
5. Calling a hedged share class risk-free. Asset risk, hedge cost and tracking differences remain.
6. Ignoring dividends and their conversion dates. Income has its own FX exposure.
7. Using mid-market FX without broker costs. The executable conversion can be worse.
8. Treating several US shares as separate currency bets. Their dollar exposure accumulates.
9. Assuming currency always diversifies. Asset and FX losses can reinforce each other.
10. Mixing quote conventions. Inverting one rate can reverse the conclusion.

Practical checklist

• Home currency is defined.
• Local asset and currency returns are reported separately.
• FX quote convention is written explicitly.
• Purchase, dividend, fee and sale cash flows use matching rates.
• Broker spread and conversion fees are included.
• Trading currency is separated from economic currency exposure.
• Hedged or unhedged status is confirmed from fund documents.
• Hedge costs and tracking differences are understood.
• Asset and FX gains and losses are stress-tested together.
• Total portfolio currency exposure is aggregated.
• Position size remains acceptable under an adverse combined scenario.

The Money Man View

An overseas asset is also a currency position unless the exposure is deliberately hedged. Evaluate the local investment thesis and the home-currency result separately, then combine them with realistic FX conversion costs. Currency can help or hurt, but it should appear explicitly in the risk budget rather than becoming an explanation after the trade.

Educational risk disclosure: Exchange rates and asset prices can move sharply and in the same adverse direction. Currency hedges introduce costs and may be imperfect. The examples are simplified and exclude personal tax circumstances. This article was prepared with AI-assisted research and writing under The Money Man editorial process.