ICUMSA (International Commission for Uniform Methods of Sugar Analysis) grading measures the colour of sugar crystals — specifically how much light passes through a sugar solution — and is used as a proxy for refinement level.
A lower ICUMSA number means whiter, more refined sugar. ICUMSA 45 is a common specification for premium white refined sugar, while ICUMSA 100–150 covers standard white sugar grades used widely in food manufacturing and food service.
Raw cane sugar sits at the other end of the scale, with a much higher ICUMSA value and a noticeably darker colour, reflecting less processing.
When requesting a quote, specifying the ICUMSA grade you need (rather than just "white sugar") helps avoid mismatched expectations on colour and refinement level once the shipment arrives.
Related to: sugar