UnitFlip – Unit Converter

A converter you open, use for four seconds, and close. UnitFlip does one thing: you type a number, and the answer is already there. No convert button, no waiting, no splash screen. It opens on whatever you converted last, with the number pad up. THE ANSWER AS YOU TYPE Two cards, one number pad. The top card is what you are converting; the bottom card is the answer, and it updates on every keystroke. Underneath sits the plain equivalence, so you can see the rate itself: 1 cm = 0.393701 in. The swap key flips the pair and keeps your number. 13 CATEGORIES, NO SIGNAL NEEDED Length, Mass, Temperature, Volume, Area, Speed, Time, Data, Energy, Power, Pressure, Fuel economy and Angle. These are defined constants, so they work on a plane, in a basement, in a supermarket aisle with no bars — for good, with no connection ever required. THE MATHS IS DONE PROPERLY Two categories break if you convert them by simple multiplication, and most cheap converters get them wrong: • Temperature is a scale with an offset, not a ratio. 20 °C is not "twice" 10 °C. UnitFlip handles Celsius, Fahrenheit, Kelvin and Rankine correctly — and yes, −40 °C is −40 °F. • Fuel economy runs backwards. Halving your mpg doubles your L/100km. UnitFlip converts mpg (US and UK), km/L and L/100km as the inverse relationship it actually is. Answers are formatted the way a person would write them — 39.3701, not 39.370078740157481 — with thousands separated and trailing zeros dropped. 166 CURRENCIES, AND AN HONEST DATE Exchange rates are daily, and this app says so. The freshness chip always tells you where the numbers came from: "Updated 2h ago" when they are current, or "Offline — rates from Aug 28" when they are not. When the rates are not current, the answer is marked approximate rather than presented as exact. Every free converter caches its rates. Most of them just pretend the number is live. This one shows you the date and lets you decide whether it is good enough. The app also ships with a real rate table built in, so currency converts on the very first launch, before it has ever reached the internet. WHAT IT DOES NOT DO • No account, no sign-up, no email • No ads and no upgrade tier — every category is there from the first launch • No analytics and no tracking • No cryptocurrency. Crypto moves too fast for cached rates to be honest about • Nothing you type ever leaves your phone The only network request UnitFlip ever makes is fetching the day's exchange rates. It sends nothing with it. GOOD TO KNOW The unit pair is remembered separately for each category, so if you always convert cm to inches, that is what is waiting for you in Length next time. The currency picker has a search box and an A–Z index, because 166 rows is a lot to scroll.