Units Converter & Calculator is a unit converter, a physical constants reference, and a small learning app in one. It converts more than 200 units across more than 30 categories, works offline, and includes a library of more than 180 physical constants with plain explanations of what each one means and how it is used.

It is made for students learning physics and chemistry, engineers and scientists, professionals who need quick conversions during the day, and anyone who regularly works with units and constants. Because it works without a network connection, it is useful in a classroom, a lab, a workshop, or on the road.

The converter covers categories including weight, temperature, distance, speed, volume, energy, and pressure, among many others. Conversions happen in real time, so the result appears as you enter a value, with no extra button to press. Every conversion is saved automatically to a history that is organized by category and easy to read, so you can come back to an earlier calculation without typing it again. The interface is keyboard-friendly and includes real-world reference examples to help you sense whether a result makes sense.

The physical constants library is where the app goes beyond a typical converter. It holds more than 180 constants, covering fundamental constants, particle physics, thermodynamics, astronomy, and more. Each entry explains what the constant is, why it is important in physics, how it is used in practice, and an interesting fact about it. Search and filters help you find any constant quickly, which makes the library handy both for checking a value and for understanding it.

The app also has three modes that turn conversion into practice. Quick Convert gives instant results when you just need an answer. Learn Mode is a guided discovery mode that uses progressive hints to walk you toward the right result, which helps when you are learning how units relate to each other. Challenge Mode tests your estimation skills by asking you to judge a conversion before seeing the answer. Progress tracking shows your learning progress, your hint usage, your challenge scores, and your completion across all categories, so students can see where they are improving.

The design is modern and clean, with smooth animations and simple navigation, and the App Store listing describes the app as working completely offline. You do not need to create an account to use it. Units Converter & Calculator is free to download from the App Store, with an optional Premium in-app purchase. It runs on iPhone and iPad and requires iOS 16.0 or later.