Skip to Content

Available Software

The Measurement Software Toolkit includes a stand-alone uncertainty calculator for Windows, a pair of Excel add-ins and a library for the R language. These software tools are all intended for developing data-processing applications that calculate measurement uncertainty.

The tools follow the recommendations of the 'Guide to the Expression of Uncertainty in Measurement', first published in 1993.

The software uses the notion of an uncertain number, an abstract data-type that represents a quantity estimate or measured value. Uncertain-number data processing algorithms simultaneously evaluate the value and uncertainty of measurement results. The technique is simple, efficient and powerful.

The following software is available on request, please fill in our Software Request Form.

GUM Tree Calculator (GTC)

The GUM Tree Calculator (GTC) is a tool for data processing with full support for uncertainty calculations involving real and complex quantities. It can process instructions typed at the command prompt, or evaluate text files containing data processing routines.

GTC is a stand-alone executable for Windows. It is closely integrated with Windows Explorer for ease of use and does not depend on any other software.

It can be used quickly on small problems, or as a sophisticated data processing tool for more demanding tasks. GTC uses the Python language for programming, which is easy to learn. An integrated development environment, with syntax highlighting and on-line help, is distributed with the calculator.

A copy of the GTC documentation is available here.


Excel add-ins for Uncertainty Calculation (SGUM and CGUM)

There are two Excel add-ins, one for real-valued quantities (called SGUM) and one for complex-valued quantities (called CGUM).

Both add-ins provide a suite of worksheet functions that can be used to manipulate uncertain numbers referenced to Excel cells. Documentation and examples are provided.

Important note about Office versions after 2003

These add-ins were developed before the release of Office 2007. We believe that spreadsheets originally written with earlier Excel versions will still execute correctly with Excel 2007 and 2010. However, if worksheets go beyond the size limits of the older Excel versions, or use features not supported in older versions, our add-ins will not work properly. We have not used these add-ins with versions of Office released since 2010.

R library

An implementation of GUM Tree for real-valued problems has been developed in the R data analysis language.

Spreadsheet Testing and Validation (Assert)

The Measurement Software Toolkit also contains a software assertion tool that can be used when testing and validating Excel spreadsheets and worksheet functions. The add-in ASSERT.xll was designed to allow an author, or checker, to incorporate dynamic tests and verification code in a spreadsheet. It provides worksheet functions to test cells, or cell ranges, and to report any failures that occur.

(Note, this add-in may not work correctly with Excel 2007 and later, see above)