About Girth

Measure length, surface and volume with a direct set of tools for making, planning and comparing.

Measure with purpose.

Girth brings 12 families of unit conversions into one accessible workspace. Select a measurement, enter a number, and compare it with other units in the same family.

How the calculations work

Each unit converts through a common base unit. Most conversions use a multiplication factor; temperature uses both a factor and an offset. Results display up to 12 significant digits and are approximate where floating-point arithmetic or rounding applies.

Definitions distinguish US and Imperial volumes, metric and mechanical horsepower, and standard and troy ounces. The notes on each converter explain the relevant conventions.

Built for everyday reference

Use these tools to compare measurements for planning, learning and ordinary tasks. Check critical measurements against an appropriate standard and your original data.

Measurement references

For the underlying definitions, consult the BIPM SI Brochure and NIST Guide for the Use of the SI.