Planning a travel budget in two currencies

Ines has a spreadsheet open, a cup of tea going cold, and a problem she hasn’t named yet. She’s a made-up traveller from Manchester, and she’s booked nine days in Japan. The flights are paid. The hotel is booked. Now she’s staring at a column that says “food” and wondering whether 1,500 means yen or pounds.

It means neither, yet. That’s the whole issue with a trip budget in two currencies. Your wages, your savings and your card statement speak one language. The ramen shop speaks another. Somewhere between the two, a rate quietly decides how far the money goes.

This guide is about that gap: how to think in both currencies without losing track, how big a buffer to carry, and what a moving rate really does to a plan. (If you want the spreadsheet mechanics, line by line, there’s a separate guide on building a trip budget in a foreign currency. This one is about the two-currency problem itself.)

Pick a home currency and stay in it

Mixing is the first mistake. Ines writes ¥1,200 for lunch in one cell, £8 for a train in the next, and adds them. The total looks tidy and means nothing.

Choose one currency for the final budget. For most people that’s the one their bank account is in, because that’s what they’ll actually feel leave their account. Do the planning in the local currency, since that’s what the prices on the menus will say, then convert once, at the end, using a single clearly labelled rate.

One rate. Write it at the top of the sheet with the date you checked it. A pair page such as GBP to JPY shows the current rate (and JPY to GBP shows it the other way round); rates refreshed hourly, so note the day, because next week’s number may differ.

Why this matters: if you convert piece by piece, using whatever rate you remember at the time, you build in small errors that don’t cancel. With one rate and one date, at least your mistakes are consistent, and you can change one cell to see the whole plan move.

A worked example, with made-up numbers

Everything below is illustrative. The rate isn’t a forecast and it isn’t today’s rate. It’s a round number so the arithmetic is easy to follow.

She estimates ¥14,000 a day for food, local transport, small attractions and the odd souvenir. Nine days. That’s ¥126,000. She picks an illustrative rate of ¥200 to the pound.

Step	Calculation	Result
Daily spend in yen	Her own estimate	¥14,000
Nine days	14,000 × 9	¥126,000
In pounds at ¥200	126,000 ÷ 200	£630.00
Add 10% buffer	630 × 1.10	£693.00

So her “on-the-ground” money is about £630, and the number she actually sets aside is £693. That extra £63 isn’t for splurging. It’s for the two things she can’t know yet: what the rate will do, and what the payment method will cost.

Where the buffer comes from

People often treat the buffer as a vague cushion. It works better when you can name what’s in it.

Rate movement

Between the day you plan and the day you pay, the rate can shift. Nobody knows which way. Suppose, purely as an illustration, that the pound slips from ¥200 to ¥185 before Ines flies. The same ¥126,000 now costs £681.08, which is £51.08 more than she planned. If instead the pound strengthens to ¥215, the bill drops to £586.05, about £43.95 less.

That’s a swing of roughly 7 to 8 per cent in each direction, and it is a made-up one. Real moves over a few weeks are usually smaller, though not always. The honest point is that a trip bought in a currency you don’t earn in carries a bit of risk that a trip at home doesn’t.

Card and cash fees

Next comes what you pay to use the money. Card issuers commonly charge a foreign transaction fee; one US card education page describes it as typically 1% to 3% of the purchase, and a UK comparison site lists non-sterling transaction fees of about 2.75% to 2.99% on some cards, with cash withdrawals attracting a separate cash-advance fee of 2% to 3% on top. Plenty of cards charge nothing on foreign spending, so check your own, and check it this month, because terms change.

If Ines’s card did charge 2.99%, her ¥126,000 at ¥200 would cost £630 × 1.0299 = £648.84. That’s £18.84 in fees. Add the weaker-pound scenario and the bill reaches £701.45 (that’s 126,000 ÷ 185 × 1.0299). A 10% buffer on the original £630 covers both with a little left over.

The “I forgot that” slice

Last is just life. A tip she didn’t expect to pay, a rainy-day taxi, a gift. Buffers exist because estimates are always a bit too tidy.

Decide what’s fixed and what’s floating

Here’s a split that changes how risky the plan feels.

Some costs are already fixed in your home currency. If Ines paid the flights and hotel in pounds, no rate can touch them. Those belong in the sheet at face value, with no conversion and no buffer.

Other costs are floating: everything she’ll pay for in yen. Only that slice needs the rate, the fees and the buffer. A person who has prepaid 80% of the trip has very little exposure. A person paying nearly everything on the ground has a lot more.

This also tells you when to worry. If most of your spend is locked in, a rate wobble is small news. If it isn’t, it’s worth being deliberate about how and when you obtain the local money.

Cash, card or both?

For the money itself, Ines decides on a mix: a small amount of yen in her pocket on arrival, the rest on a card. The sensible bit is how she plans for each, not which she picks.

Before she leaves, she’ll check three things on the card she intends to use: the foreign transaction fee, any fee for cash withdrawals, and whether it works abroad at all. Then she writes her answer on the first line of the spreadsheet, so the plan and the facts live in the same place.

On the trip, one habit does more than any trick. When a terminal or cash machine offers to charge her in pounds instead of yen, she declines and pays in yen. That prompt is called dynamic currency conversion, and the conversion it offers is done at the merchant’s or machine operator’s rate, which tends to be less favourable. A UK consumer-money site says plainly that it’s always better to pay in the local currency. For a longer look at this one, see our guide on dynamic currency conversion.

Last, the card statement will arrive in pounds, converted by the card network and the issuer, not at the rate Ines saw on any website. Use a converter to plan, not to predict the exact figure. Even the European Central Bank, which publishes euro reference rates each working day at around 16:00 CET, says those rates are for information only and discourages using them for transactions. A published rate is a guide. What lands on your statement can differ.

Keep a running tally in both currencies

Back to the trip itself. By day three, Ines has a routine. Each evening she adds up what she spent in yen, then divides by her planning rate to see roughly what that is at home. Two columns, thirty seconds.

It’s not about precision. It’s about noticing early. If day one cost ¥19,000 against a ¥14,000 plan, she’d rather know on Tuesday than the following Monday. She can then trim or accept it, with the buffer as her reserve.

A small trick: round the rate in your head. At ¥200 to the pound, every ¥1,000 is £5. At ¥185, a ¥1,000 note is about £5.40. Anchoring on a friendly number makes quick decisions at a till far easier than punching figures into a phone.

And if she’s checking the market mid-trip? That’s fine, but it won’t change what she paid. Spend already made is made. A better rate next week doesn’t refund Tuesday’s lunch.

A short checklist before you go

Write the plan in the local currency, then convert once with a dated rate.
Separate what’s already paid in your home currency from what you’ll pay locally.
Add a buffer you can explain: rate movement, card fees, surprises.
Look up your own card’s foreign fee and cash-withdrawal fee this month.
Pay in local currency whenever a terminal offers a choice.

The laptop closes. The tea is properly cold now. Ines has one number, £693, and she knows what’s inside it. That’s a better place to start a holiday than a guess.

Sources

Checked: November 2026