The definition and use of weights and measures in Portuguese territory is prior to nationality. All the people who inhabited the territory that today is Portugal had units of measurement and used measuring instruments in their measurements.

When Portugal became an independent country, there was no breach with the weights and measures that were used by the inhabitants of the territory, so the metrological systems used in the early days of nationality were heirs to different cultures, namely Roman, of Latin language and that of the “Moors”, with Arabic language that proved to be the most influential.

The history of metrology in Portugal can be divided into 3 major periods:

• The Medieval Period, characterized by great diversity and the absence of unique standards;
• The reforms of the Modern Period, which legislate towards uniformity, characteristics of the modern, centralized state;
• The implementation of the Decimal Metric System, a precursor of the International System of Units.

The Permanent Exhibition “Weights and Measures in Portugal” allows visitors to learn a little about the evolution of these measurement systems that are part of the history of metrology in Portugal, starting from the measurement instruments used in different times, from the Middle Ages to ours days.