I’m from the USA, but I can ‘think’ in British Pounds, Euros, and Canadian dollars. In other words, I don’t have to do a mental currency conversion. I kinda know the Swiss Franc and Australian dollars as well, but I’d probably be using my phone quickly to convert into American dollars.
Shekels, dollars and euros. Shekels because it’s my currency, dollars because it’s the global currency, and euros because I travel to the Eurozone every now and then.
I’m not sure what you mean by not having to do a 'mental currency conversion", but off the top of my head I know that 1 US dollar is roughly equivalent to 1000 Korean Won, 7.8 Hong Kong dollars an 80-100 Japanese Yen. If I’m doing a transaction in those currencies I’ll make sure I know that exact conversion rate that the time I do the transaction.
Hong Kong has a “unique linked exchange rate system” (according to Wikipedia) that has keep the exchange rate at ~7.8 HK dollars to 1 US dollar since 1983 so it’s easy to remember. My guess it’s a worldwide value metric like the US dollar which all other currencies are compared/adjusted. to.
I think a lot of the memorization / mental calculation has to do with which currencies you’re used to trading in. It’s definitely true for me since most of my video purchases are from Asian countries.
My wife can’t think in any. :rolleyes:
British pounds, US dollar, Chinese RMB, Euros
But in truth, all prices are “really” in pounds to me, it’s just that converting from dollars, RMB or euros is so natural I don’t even notice I did it.
So wherever I am in the world I might exclaim something like “£7 for shower gel!?” or whatever.
American Dollars, British Pounds and Euros. I used to be able think in Canadian Dollars but that was long ago.
I think it’s about seeing a number (in dollars, euros, yen, etc.) and immediately having a mental grasp of the significance of that number without having to convert to your native currency. So for example, if you read/hear that a salaryman earns 3,500,000 JPY per year, do you think he should be buying the next round of drinks, or asking his boss for a raise? If your dinner bill is USD$11.50, do you complain to the server about their rip-off math, or chuckle to yourself about what a good deal you got?
Same thing for me with pounds and Canadian dollars, I convert it to USD automatically in my head and then think in that. It helps that they’re both close enough that you don’t have to do the hard math that results from trying to multiply or divide by more than say 1 1/3 but not a whole number.
Sure but the “thinking” part is going to be completely dependent on where you are at the moment. Getting on the Metro at Sunset and Vermont is economically a different prospect from getting on the Transmilenio in downtown Bogotá, so thinking “dos mil pesos” isn’t going to have the same meaning anyway.
I don’t travel anymore but when I did, Cambodia was easy (most things are priced in US$, which has been about as 4000 riel for many years) and so was Singapore (“if it seems a little dear, remember that these are S$, not US$.”) Not making major purchases, the exact price hardly mattered.
So I think in both Thai Baht and US Dollar, converting one to the other if it adds perspective. Despite that the arithmetic is easy for me, I respond differently to the different currencies. Pay ฿400 for lunch for two and expect it to be delicious. What kind of lunch for two will $12 (the same amount) buy in the U.S. these days? Middle-classers are quite proud to earn a ฿65,000 baht monthly salary here (quadruple what young college graduates earn) but is less than $2000 US.
The Thai baht is still implicitly pegged, I think, to a dollar-dominated basket. This mean the ฿/$ fluctuates little and I needn’t bother checking exchange rates. Contrast this with Brits whose ฿/£ is on a roller-coaster pegged to Brexit drama.
I can think in yen almost better than in dollars since I keep thinking in 1990 costs!
I have NTD (New Taiwanese Dollars) down as well now.
But that’s part of the equation. Just like you know that food in an airport will cost more than at a food court in a shopping mall.
The only place where I need to convert Euros to Dollars typically offers a one-to-one exchange to attract US tourists.
I can do US dollars to UK pounds and vice-versa.
I can also do US pounds to everyone else kilograms and vice-versa.
None, nowadays. Back when I traveled in Europe for a living, I could easily shift from dollars to marks, rubles, kroner, francs, guilders, Austrian schillings, and pounds. Not to the penny, of course, but could ballpark it pretty close.
It’s all about the U.S. dollar, baby.
Everything else is funny money.
Yep! I have a safe deposit box, but very little I really need to keep safe. I just like having one, and it’s cheap. It’s also fun to occasionally access. I have a little lead soldier, a couple of fortune cookie slips, but it’s mostly currency brought back from my vacations. Bills from Jamaica, Canadia, various Caribbean islands, France, Germany, etc. Also a Bill from Iraq featuring Hussein’s visage. Maybe $40 total.
Anytime safe deposit boxes come up in conversation (it happens) I mention my local bank, which offers a decent sized box for $10 a year. Invariably someone asks what I keep in it and I can honestly answer, furtively, “it’s not entirely legal, but I have foreign currency in it.” 
Yen, dollars (US, Canadian, Australian) and Euros are all basically the same, except you move the decimal place for Yen. Yeah, some are “bigger” than others, but I am not going to decide whether this restaurant is out of my price range because it costs 5% or 10% different from what it looks like.
Pounds, sadly only buy about as much as dollars, despite being a lot more expensive. At least, that was my most recent experience. I haven’t checked the exchange rates or local prices lately.
I remember my first trip abroad as an adult, there was a some service offering to help me convert Greek Drachmas into US dollars, and save the trouble of figuring out the conversion. At the time, I could buy 101 drachmas for a dollar. I did not spend a lot of time thinking about the conversion. 
(I did in Italy, where there was a factor of 7 and a lot of zeros involved.)
I’m bilingual in Fahrenheit and Celsius, which I find a lot more useful.
In the past 3 weeks I have used Polish Zloty, Ukranian Hryvnia, Czech Koruna and Euro, and have been able to successfully mentally convert them back into U$D within a small margin of error, which given my abject lack of innate math skills combined with my “enthusiasm” for grain-based adult beverages is no small feat, if I do say so myself.
It is actually not that hard, as in my 3 years of living here in Krakow, the Zloty has basically been pegged 4 to 1 against the Dollar within a few cents either way depending on economic factors that are way over my head, so to me, a Zloty is a quarter, making mental conversions automatic after a few days, and the Czech Koruna is similarly pegged to be about 25 to 1 against the Dollar, which is a little trickier, but after a few days also becomes automatic (it helps that as a general rule, a large draft beer in a non-touristy Krakow or Prague bar is about $1.25 depending on the specific spot you are drinking at, possibly a little less, though you can easily pay considerably more if you are looking for something upscale)
With Euro, for some reason, I think of it “backwards” in that mentally I consider 1 Euro to be a little less $1.20 rather than 1 Dollar is 80 cents Euro, I am not sure why but that is how I mentally tabulate my spending in the Euro Zone.
In Lviv, a gorgeous (now) Ukranian city that used to be a cultural center of Poland until the end of WWII, the Hryvnia was 28 to 1, but what I found most interesting was that they have paper 1 Hryvnia bills, meaning they were worth a little more than 3 cents each, which while thinking about it after several of the aforementioned grain-based beverages, I decided if you wrote to Parker Brothers and asked them for a replacement set of Monopoly money, it would likely cost you more than that.