Top 4 C++ units-of-measure Projects

mp-units

2 942 9.8 C++

The quantities and units library for C++

Project mention: Is it just mean, or is C# easier to learn than JavaScript or even PHP? | /r/dotnet | 2023-12-06

It's not the type system you're complaining about, though. It takes a bit of work but you can write types that include units information with no loss of performance.
SI

0 481 8.0 C++

A header only C++ library that provides type safety and user defined literals for physical units (by bernedom)
InfluxDB

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au

1 275 8.2 C++

A C++14-compatible physical units library with no dependencies and a single-file delivery option. Emphasis on safety, accessibility, performance, and developer experience. (by aurora-opensource)

Project mention: I'm a beginner making a library for unit conversion, contributions are welcome | /r/cpp | 2023-04-21

Be sure to check this one, too https://github.com/aurora-opensource/au
konverter

0 1 0.0 C++

Flexible engineering and scientific unit converter.

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2023-12-06.