BIDMAS is a rule for remembering the agreed order of operations in Maths. BIDMAS stands for Brackets, Indices, Division and Multiplication, Addition and Subtraction. The order you should do your calculations in is: Brackets; Indices; Division and Multiplication (start on the left and work them out in the order that you find them); Addition and Subtraction (when only addition and subtraction are left in the sum, work them out in the order you find them - starting from the left and working towards the right). Indices are also known as 'orders', which gives rise to the use of the term BODMAS (where the O replaces the I) as an alternative to BIDMAS.