Use libSI to apply math in C++ correct, precise, and convenient. Top features are:

Strong type-safety for datatypes, constants, formulas, and literals (can't add a mass to a length).
High precision by FP 64-bit, calculations on SI base units only, and CODATA 2022 constants.
Maximum speed without runtime overhead. It just compiles to simple doubles.
Supports SI units, Imperial units, digital units, astronomical units, and a lot more.
Modern C++ 17: header-only, own namespace, no external dependencies.
Cross-platform support for Linux (clang/gcc, x86/arm) and Windows (VS2017-VS2026) with CMake support.

🔎 Usage Example

#include <SI/core.h>
using namespace SI;
 
int main() {    
    mass m   = 1_oz;
    energy E = m * square(constant::speed_of_light_in_vacuum);
    std::cout << "The potential energy of a single ounce is: " << E << std::endl;
}

🧱 Core Building Blocks

Datatypes like SI::length in <SI/datatypes.h>
Units such as SI::meters in <SI/units.h>
Literals like 100_m in <SI/literals.h>
Constants such as SI::constant::lightyear in <SI/constants.h>
Formulas like SI::formula::wavelength() in <SI/formulas.h>
Conversions such as SI::to_string() in <SI/conversions.h>

📦 Other Components

47 Examples writing this console output in subfolder 📂examples
Unit tests executed at compile-time and on each commit by GitHub Actions in <SI/tests.h>
Datasets like chemical_elements in 📂datasets (using libSI datatypes and units)
Documentation in the API reference manual

💡 Q & A

What is SI? It's the International System of Units which is made up of 7 base units that define the 22 derived units.

What is CODATA? It's the Committee On Data of the International Science Council (ISC). It publishes fundamental physical constants on a four-year cycle. Latest update was CODATA 2022 which is equal to: NIST SP 961 (May 2024).

What are use-cases for libSI? Applied math such as simulations, simulators, scientific calculations, games, etc.

What are numbers like 1.2e23? It's the scientific notation in C/C++ for 1.2 x 10²³, the letter 'e' or 'E' represents the 'times 10 to the power of' part.

How to import or export numbers and string? See the code examples in examples/conversions.cpp.

Where are the list of references? References are always listed at the end of each source code file.

🤝 Contributing

Contributions, suggestions, and improvements are welcome!
Open an Issue if you encounter bugs or have feature ideas.
Create a Pull Request if you'd like to improve something.

📜 License & Copyright

This open source project is licensed under the CC0-1.0 license. All trademarks are the property of their respective owners.