The Hidden iPhone Calculator Feature Every Cook and Traveler Should Know

Every once in a while as I’m boarding a flight, wandering an unfamiliar city, or trying to figure out if a bottle of single malt is the bargain of a lifetime or costs more than my student loan, I think back to how I handled such matters in the time before smartphones. In short: fumbled for the paper ticket I’d found buried under a stack of mail, tried not to weep as I circled the wrong block for the 10th time in search of my hotel, weathered a stress-related eyelid twitch attempting to remember the most recent exchange rate, and buying the booze no matter how the math worked out.

But on my recent trip through Copenhagen airport Københavns Lufthavne, I had plenty of time to lollygag in the duty-free aisles before my flight (thanks to having my travel documents on my phone and my route mapped out) and came upon my holy grail — an airport-exclusive liter of Ardbeg Smoketrails Napa Valley Edition. The single malt Scotch was 619 DKK, and I initially panicked thinking it was dollars and not Danish krone. Rather than fire up the calculator app and multiply by 0.15, I used an iPhone function that you may not know about.

How to use the conversion function in your iPhone calculator app

Open up the calculator app, but instead of doing that basic math, long-press the calculator icon at the bottom left. A menu will pop up with the options Basic, Scientific, and Math Notes, with a toggle next to the word Convert. Turn that option on, long-press the symbol all the way to the right of the top or bottom number (it looks like two carats stacked together) and long-press that. 

Discovering this functionality was like finding a whole secret room in my house. That day, not only could I find that 619 DKK was $95.40 rather than the $92.85 my rough math would have shown (the exchange rate is dynamically updated by Yahoo Finance), I could determine if my suitcase fit the weight parameters in kilograms or how many milliliters of liquid I was carrying, with those conversions to the metric system a tap away.

This function has been a lifeline for me in the kitchen since I’m constantly looking up conversion tables or Googling how many fluid ounces are in a tablespoon, how many milligrams are in a pound, what temperature to set my oven to if I’m using a recipe from another country — the list goes on. There’s a search bar at the top for quick access to specific measurements (“ounce” yields results for fluid ounce and UK fluid ounce under Volume and ounce under Weight), or I could side-scroll for options to convert Angle, Area, Currency, Data, Energy, Force, Fuel, Length, Power, Pressure, Speed, Temperature, Time, Volume, and Weight.

To get back to the regular calculator function (which will seem so mundane now), just long-press that calculator icon again and toggle the Convert option off. The Scotch — all 33.814023 fluid ounces of it — was an absolute steal.