Best Free Unit Converters to Use in 2024 

Whether you notice it or not, converting units is an essential part of everyday life. You convert units to exchange currency, analyze data, compare quantities, and even bake a cake!

But if you don’t have exact unit conversions memorized, then a unit converter is a must have tool to add to your arsenal. On top of that, which ever unit converter you use needs to be user-friendly, accurate, and contain a wide range of conversions.

Don't know where to start looking for one? To make the search easier for you, we’ve dug up some of the best you can find across various platforms: 

• iOS
• Android
• Web
• Windows
• Mac

Sift through our list below for a unit converter calculator for any platform you need, whether online, on your desktop or on your mobile device.

Best free unit converter apps for iOS

There’s nothing more useful than having all the tools you need when and where you need them. If you need to convert units on your iPhone or iPad at the ready, try the following apps.

1. Unit Converter

This is the free version of Units Plus Converter. This unit converter offers a well-designed interface with unit converters for 12 categories. Whether you're a student, engineer, or just dealing with math and conversions, this app is a versatile solution, available offline, eliminating the need to remember complex formulas.

Rating on App Store: 4.8 ⭐ (140.6k ratings)
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2. Metric Conversion tool

This is the free Unit Converter App from metric-conversions.org. The app offers an easy-to-use interface, offline functionality, and popular unit conversions, including currencies with live exchange rates. Access your favorite unit converters quickly and convert units in categories such as mass, length, volume, time, and more.

Rating on App Store: 4.8 ⭐ (13.6k ratings)
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3. Unitify - Unit Converter

Unitify is a swift and user-friendly unit and currency converter. Simply input the value you wish to convert, and the app instantly displays all related units in a single list. The app includes a built-in calculator for direct calculations.

Rating on App Store: 4.8 ⭐ (415 ratings)
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4. Converter of Units

With almost 500 units in 37 measurements, including date calculators and tank capacity options, Converter of Units is one of the most comprehensive unit converter apps on iOS for free. Notable features include quick notes, shareable results, keyboard shortcuts, multiple windows, and light and dark modes. 

Rating on App Store: 4.9 ⭐ (32 ratings)
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Best free unit converter apps for Android

We’ve got Android users covered, as well, with a few of the best unit converters available. All the apps below provide seamless functionality for users converting measurements on the go.

1. All-In-One Calculator for Android

A free, comprehensive, and user-friendly calculator and converter. All-In-One Calculator for Android offers features from calculations to unit and currency conversions. While the app contains ads and in-app purchases, it comes with over 75 calculators and unit converters, making it super handy for a number of industry and general needs.

Rating on Google Play: 4.7 ⭐ (142k ratings)
Downloads on Google Play: 10M+
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2. US-Metric/Imperial Converter

This free app offers a user-friendly interface, allowing you to easily convert various units for daily tasks, DIY projects, and more. Streamline how you convert units. Notable perks include no ads, no account creation needed, and support for 26 languages.

Rating on Google Play: 4.9 ⭐ (1.64k ratings)
Downloads on Google Play: 50k+
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3. Unit Converter

Unit Converter features an intuitive and simple UI designed for casual users. It includes essential unit sets categorized into basics, living, science, and miscellaneous. The app displays different unit sets based on the user's country and offers additional units upon request. This app is free but contains ads.

Rating on Google Play: 4.4 ⭐ (220k ratings)
Downloads on Google Play: 10M+
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4. All Unit Converter & Tools

All Unit Converter & Tools is a free unit converter calculator app, offering a ton of functions and unit conversions. As a Swiss army knife unit converter, the app includes a scientific calculator, compass, speedometer, periodic table, day counter, and more.

Rating on Google Play: 4.9 ⭐ (746 ratings)
Downloads on Google Play: 50k+
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Best free web-based unit converters

For those who need an accurate conversion calculator while working online or in a browser, there’s no shortage of web-based unit converters out there. Check out our top picks below.

1. Converticious

Converticious performs unit conversions for temperature, volume, distance, weight, area, data, time, and speed. This web-based unit converter features useful resources, as well, such as a list of unit conversions, a calculator, and even conversion worksheets you can download.

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2. Convertworld.com

On top of a comprehensive list of unit converters, Convertworld.com also puts the spotlight on more general conversion needs. You can get unit conversions for shoe and clothing sizes, TV and monitors, pregnancy stages, and even tire sizes! Another unique quality? The site supports and accommodates more than 10 languages.

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3. Unit Converter

With a ton of possible unit converters out there, Unit Converter aims to be one of the most comprehensive online. It offers converters under 9 separate categories and lists the most common ones for quick access. Get unit converters for light, magnetism, electricity, engineering, and more!

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4. Free Online Unit Converter

Not only is Free Online Converter free, accurate, and safe, but it also offers up a clean interface, the ability to customize your widgets, and a wide range of conversions. Its mass and length unit converters, for instance, offer up international and highly niche unit conversions. Perfect if you’re looking for rare conversions and a good user experience.

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Best free unit converter for Windows 

If you're a Windows user, then you know that the Windows calculator serves as the best free unit converter at your fingertips. It’s convenient, simple, accessible and free. With the Windows utility, you can convert a long list of unit types:

• Currency
• Length
• Volume
• Energy
• Temperature
• Time
• Speed
• Weight
• Data
• Area units

How to convert units on Windows 

If you’re looking to convert units that fall under any of the above categories, here’s a quick look at how to quickly convert units with the Windows Calculator app:

1. Open the Calculator app.

2. Click on the 3 horizontal lines in the top left corner to open the menu of options.

3. Under the “Converter” section, select a unit conversion tool.

4. Select a unit to convert from in the first drop-down menu.

5. Choose a unit to convert your entered value to in the second drop-down menu.

6. Enter the number value to convert.

The Calculator app will instantly provide you with the conversion. To enter a new value, simply delete the current number and enter in a new one.

Best free unit converter for Mac 

If you’re on a Mac computer, you also have a native calculator tool already built in. The Mac calculator is the best free unit converter for macOS users when you’re in a tight spot. Though a single utility, the calculator can support a good list of unit conversions:

• Area 
• Currency 
• Energy or Work 
• Length
• Power 
• Pressure 
• Speed 
• Temperature 
• Time 
• Volume 
• Weights and Masses

How to convert units on Mac 

To use the Calculator app as a unit converter on Mac, follow these steps:

1. Launch the Calculator app on your Mac and enter a number.

2. From the menu bar, go to Convert.

3. Select the category of unit you want to convert, the unit you want to convert from and the unit you want to convert to.

4. Click on the Convert button. The Calculator app will automatically convert your units.

Streamline PDF data analysis and unit conversions with ease

PDF files often contain data from different sources, requiring accurate unit conversions to standardize inputs and streamline information processing.

This is particularly crucial when comparing financial reports, scientific research, technical blueprints, or other data-rich PDFs, ensuring consistency in the analysis across various documents.

Inconsistencies in units across datasets can significantly impact decision-making and financial outcomes. Thankfully, tools like Xodo offer a solution, enabling you to convert and manipulate PDF data instantly.

For example, Xodo's free online PDF to Excel converter lets you export PDF data to an Excel spreadsheet. This saves time and allows for easier analysis and more precise unit conversion, minimizing potential errors in the process.

There you have it — a comprehensive list of the best free unit converters to try out on iOS, Android, web, Windows, and Mac. Now armed with Xodo as well, you can more efficiently analyze your PDF data.

All 30+ Xodo tools are accessible and universally compatible, allowing you to work anytime, anywhere. Whether you’re calculating profits in Excel or consolidating reports from international departments, you can be consistent and accurate with the units being used right on the spot.