Introduction

Physical Quantity is a single-header c++ library providing compile-time SI unit consistency.

Physical Quantity implements most of the International System of Units (SI), with a few exceptions (angles, for example). Once you start using it, your compiler will take care of making sure all units are converted properly, at compile time.

Here's an example:

  // When I am in a hurry, I walk
  Length<double> length = Length<double>::kilometer(1.0);
  // in
  Duration<double> time = Duration<double>::minute(10);

  // Then my speed is
  Velocity<double> velC = length / time;

  std::cout << "My walking speed: " << velC.meterPerSecond() << "m/s, "
   << velC.kilometerPerHour() << "km/h, "
   << velC.knots() << " knots.\n";

Basically, the library provides template types to wrap the containing values and do the proper conversions.

When using the variable, there is no need to worry about its unit: it is enough to know its nature (a length, a duration, a voltage,...).

Other libraries solving a similar problem

• boost units: more complete and flexible, more complicated to use.
• unit lite: allows you to define your own units, but less convenient for SI.
• Poco Units.

What quantities/units are supported?

Most of SI and part of the imperial system are supported, with both British (meter) and American (meter) spellings.

See the full list

What operator is supported?

• multiplication with another quantity *
• division /
• addition +
• subtraction -
• multiplication with a scalar (with quantity.scaled(scalar) or scalar * quantity)
• sqrt
• fabs
• Trigonometry: cos, sin, tan
• isNaN, isFinite

How to use Physical Quantity in my project?

You need just a single file: PhysicalQuantity.h. Make sure you can include it, either by copying it in your project or add the containing folder to the include directories.