I Tried a Bunch. These Are the Best Unit Converter Apps for iPhone

Ever tried following a recipe that lists everything in ounces, but your kitchen scale only shows grams? Or maybe you measured your room in feet but need to order furniture in centimeters.

These small unit conversion issues pop up more often than you’d expect. From converting weight and length to checking fuel efficiency or data units, having a good converter app on your iPhone really helps.

It saves time, avoids guesswork, and ensures you always get the numbers right. Let’s explore the top unit converter apps worth downloading for your iPhone.

What Makes a Great Unit Converter App?

There’s no one-size-fits-all solution. Some people want a simple, easy-to-use app with a clean interface, while others look for advanced features and detailed information. Some need offline access, while others prefer real-time currency updates.

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However, most apps on the App Store are either filled with ads or fail to offer even the most basic and useful unit conversions. That’s why I tested over 30 unit converter apps—handpicking the ones that are clean, fast, packed with useful features, and actually deliver what they promise. We follow a rigorous app testing methodology to ensure every recommendation is unbiased and reliable. Each app in this list offers something unique and distinct. Select the one that best suits your needs.

1. Apple Calculator App – Built-In and Ad-Free

If you’re running iOS 18 or later, you already have a unit converter in your pocket. The Apple Calculator app now supports conversions for things like:

• Angle
• Area
• Currency
• Data
• Energy
• Force
• Fuel
• Length
• Power
• Pressure
• Speed
• Temperature
• Time
• Volume
• Weight

This covers the basics for most people. There’s no need to download another app if all you need is to check conversion rates occasionally. For currency, it fetches real-time exchange rates from Yahoo Finance. It has no ads or subscriptions. Simply tap the calculator icon at the top, toggle the Convert option, and switch between units directly within Apple’s calculator. 

Also Check: Best Calculator Apps for your iPhone

2. Unit converter, convert metric – Conversion Calculator for all kinds of units

This app doesn’t stop at inches and Celsius. It goes way beyond—converting everything from electricity and area to torque, ring sizes, clothing sizes, and shoe sizes, as well as even oddly specific items like GPS coordinates, wind speed, and running pace. With over 60 categories, it easily beats what Apple’s built-in app offers.

What makes it even better is how it shows all units in a category at once. Just type “1 kilometer” and you’ll instantly see the value in miles, feet, inches, and more—no need to switch manually. It’s super useful for learning, or if you’re just curious about how 5 kg translates to pounds, ounces, or stones. Even its widget gives you an overview of all the units at once.

The catch? Some categories are locked behind a $23 annual subscription, and the free version includes ads.

3. CalConverter – Focus on What You Actually Use

Similar to the Conversion Calculator, this app allows you to view multiple unit values simultaneously. Type in “1 kilometer,” and you’ll instantly get the equivalent in miles, feet, inches, and more—all in one go. What makes it even better is the customization. If you’re cooking and only need conversions for tablespoons, cups, and ounces, you can hide the rest and keep things tidy. You can even rearrange the units to place your most frequently used ones at the top.

It supports all the essential categories—speed, temperature, volume, weight, data, energy, force, frequency, area, and more. But there’s a catch. Most categories, including common ones such as area and volume, are locked behind a Pro subscription that costs $12 per year. And yes, there are ads too.

4. Unity – Measure Things with Football Fields and Blue Whales

If you like measuring things in football fields, blue whales, or Coke bottles, this app is for you. It provides you with quirky, real-world comparisons that most converter apps won’t even consider. Ever wondered how many liters fit in five bathtubs? Now you can find out.

It also covers all the basics—angles, distance, mileage, area, data, weight, volume, and more. You can save your favorite conversions too, so they’re always just a tap away.

The app is simple and easy to use. It does have ads, but you can remove them with a one-time payment of $3.99, which also unlocks unlimited favorites.

5. Morpho – Check Currency Rates Without Unlocking Your Phone

This app handles all the usual units of measurement, including area, weight, temperature, and volume. But what makes it stand out is its currency conversion widget for the lock screen. You can check live exchange rates without even unlocking your phone—super handy if you’re traveling or working with international clients.

It supports 170+ currencies and updates rates every hour. You can also pin your most frequently used conversions to the home screen for quick access at any time.

The downside? Free users receive daily currency updates, but the app displays ads. To unlock hourly updates and remove ads, you’ll need the Pro version, available for $4.99 per year or a one-time payment of $24.99.

6. Elk Currency Converter – Your Travel Buddy for Quick Price Checks

If you’re traveling and need to quickly check prices in your native currency, this app is a lifesaver. Instead of typing numbers, you just swipe through values. Say something costs 9.6k Japanese Yen—you can swipe to 9k, tap it, and instantly see how much that is in your currency. It’s perfect for shopping, dining out, or staying on top of your spending abroad.

You can even add a Siri shortcut. Simply say “JPY to USD,” and it opens right up.

The app keeps things simple—that’s its biggest strength. Clean interface, easy to use, and no clutter. However, most countries are locked behind a monthly subscription of $2.99. But you can use the app only when you’re traveling and cancel the subscription when it’s not in use.

7. Currency Converter – Dedicated Currency and Crypto Converter App

This one’s a dedicated currency converter app, built for more than just checking live exchange rates. You can view price history through interactive graphs, track popular cryptocurrencies, and even monitor metals like gold—all in one place. You can also pin your favorite currencies to the home page and add a watchlist widget right to your iPhone’s home screen.

The free version includes ads and limits the graph view to just a day. To unlock full graph access, you’ll need a $6.99/week subscription.

As an alternative, there’s another app called World Currency Converter. It also shows ads, but lets you remove them with a small one-time payment of $0.99. Please note that it doesn’t support cryptocurrency.

Also check out: Best Money Transfer Apps on your iPhone

How to Choose the Right Unit Converter App

Not sure which one to install? Here’s a quick guide:

• For basics (length, weight, etc.): Apple Calculator or CalConverter
• For unique units (torque, running pace): Conversion Calculator
• For quirky comparisons: Unity
• For travelers: Elk or Morpho
• For currency, crypto, and charts: Currency Converter by Agnes Frances

Final Thoughts

You don’t need to memorize conversion formulas or keep opening Google every time you travel, shop online, or measure something in a different unit. Whether you need fast currency updates, niche scientific units, or just a better way to convert cups to grams, these iPhone apps have you covered.

Pick the one that fits your needs and let your iPhone do the math from now on.

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