Part of the fun of visiting another country is savouring how different everything is from home.

But navigating the unfamiliar aspects of daily life in another country – like currencies, clothing sizes and food ingredients – can be challenging. Luckily, a number of iPhone and Android apps can help you cross those cultural divides.

In the below list of common cultural challenges, I favoured apps that don't require an Internet connection, because data connections outside of your home country can be violently expensive. Download these suggestions before your next trip and you'll be passing for a local in no time.

Decoding your clothing size
A size 7 pair of men's Reeboks in the UK is a size 40.5 in France and a size 8 in Canada. But not all shoe and clothing labels list sizes internationally. Among the iPhone apps that convert sizes, I like Clothes ($0.99) the best for its simple interface. Roll an on-screen dial to pick your size for clothes, shoes and other items, and choose between six language settings. (Note: This app converts sizes; it does not promise that a garment will fit you.)

Among Android apps, the best is Clothing Size Conversion (free). Its interface is similarly simple but English is its only language option.

Decoding menu items
Avoid mistranslation of unfamiliar menu items by whipping out the Foodict Food Dictionary iPhone app ($1.99), a database of hundreds of common cooking terms worldwide. While missing some terms ("trotter gear", "sea purslane"), it is superior to similar apps in its category because it auto-suggests as you attempt to spell a word, and uses little flag icons to indicate the nationality of items. We haven’t found a comparable Android app yet.

Decoding mysterious ingredients
Nervous about eating something that has an unfamiliar ingredient? Allergic to peanuts? The Don’t Eat That iPhone app ($1.99) has the skinny on more than 1,900 ingredients, including ones banned in some countries under different names. The app covers food in the US and in Europe. There unfortunately is no Android version yet.

Decoding immunisation advice
The Healix Travel Vaccination iPhone app (free) helps you figure out if you need inoculation shots before your vacation. Tell the app which countries you'll be visiting, and it fetches a list of suggested vaccinations. Healix, a UK medical services provider, collected the data on 196 countries for this app.

An equally good app on the Android platform is Relief Central (free), which bundles together authoritative advice for international travellers about health risks from the Centers for Disease Control and Prevention Yellow Book, and the Central Intelligence Agency World Factbook.

Decoding foreign signs
Word Lens
(free) is a deservedly hyped app that allows you to point your iPhone’s video camera at foreign words and see an instant translation superimposed on the live image. What traveller wouldn't like the sci-fi immediateness of its translation, which spares you from flipping through the pages of a printed phrase book? The app translates between Spanish and English, but more languages are in the works. While the app is free, you have to purchase a dictionary ($10) for each language. There is no comparable Android product.

Decoding common phrases
In real-world situations, it feels to awkward to stop, open up an app and look up a phrase, which is why we like Word Lens. But if you find yourself in a crunch and Word Lens can't do the trick, the iPhone and Android iTranslate app (free) is the next best choice, because it covers more than 50 languages, with thorough listings of vocabulary and handy phrases. The app also claims to translate phrases spoken into an iPhone's or iPad's microphone using built-in voice-recognition software, though this function needs improvement to be useful.

Decoding a currency's value
There are plenty of currency conversion apps out there that keep you up to date with current exchange rates. I like Oanda's best because its data comes from one of the world's largest currency databases and it has a slick, straightforward interface (iPhone and Android, free). The app doesn't require an Internet connection to operate but it relies on data downloaded from its most recent online connection.

Decoding temperatures and other measurements
The least powerful lobby in Washington, DC, may be the one attempting to convert the US to the metric system. In the meantime, America's unwillingness to use the same measurement system as the rest of the world requires international travellers to make tedious conversions between metric and the imperial/US system. Which is why thoughtful developers invented ConvertMe (free), an iPhone app that helps travellers convert temperatures between Celsius and Fahrenheit to understand a weather forecast, convert litres and gallons to figure out how much fuel a car requires and convert metric and imperial units to make sure your bag stays within an airline's luggage requirements. The best equivalent Android app is ConvertMe (Beta) (free), which does all the same essential conversions a traveller might need. (Despite bearing similar names, the two apps are made by different developers.)

Decode… where the bathrooms are
Everyone has had that frustrating moment of trying to find a bathroom in an unfamiliar city. In some countries, it's customary for all cafes, bars and fuel stations to have bathrooms available, even for non-paying guests, but in other nations you're expected to use facilities dedicated to the public. To avoid confusion, download the Toilet/Bathroom Finder app (iPhone and Android, free), which lets you view nearby bathrooms in a list or map format. The information comes from users, so it can be hit or miss. Yet I've found that the bathroom listings on this app are more accurate overall than the ones on its main competitor app, SitOrSquat, and it's spot on most of the time when used in the US and Europe.

Sean O'Neill is the tech travel columnist for BBC Travel