Levels of Compression for Compression Socks Explained

Levels of Compression for Compression Socks Explained
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Compression clothing uses millimetres of Mercury (mmHg) when it comes to measuring the levels of compression (pressure). 1mm of mercury = 1/760 of an atmosphere of pressure. In science, the pressure is measured in Pascals (1 mmHg = 133.322367415 pascals); however, in medicine the standardised unit of compression level is measured in mmHg.

Compression Classes
While mmHg is a standardised unit of measure for the strength of compression, when it comes to classes of compression, there is no universal classification. There are two most common classifications (AFNOR and RAL) as well as the BSI classification.

The AFNOR standard comes from a French body for standardisation and normalisation (Association Française de Normalisation) and has the following break down of classes:

Class 1: 10-15 mmHg (Very light compression)
Class 2: 15-20 mmHg (Light compression)
Class 3: 20-36 mmHg (Moderate compression)
Class 4: 36+ mmHg (Strong compression)

The RAL standard comes from a German body and is generally used EU-wide:

Class 1: 18-21 mmHg (Light compression)
Class 2: 23-32 mmHg (Moderate compression)
Class 3: 34-46 mmHg (Strong compression)
Class 4: 47+ mmHg (Very strong compression)

The BSI standard comes from the British Standards Institute:

Level 1: 14 - 17 mmHg (Light Compression for Active Use)
Level 2: 18 - 24 mmHg (Moderate Compression for Active Use)
Level 3: 25 - 35 mmHg (High Compression for Active Use & Recovery)