A system includes a fixed-point accumulator for storing numbers in an anchored fixed-point number format, a data interface arranged to receive a plurality of weight values and a plurality of data values represented in a floating-point number format, and logic circuitry. The logic circuitry is configured to: determine an anchor value indicative of a value of a lowest significant bit of the anchored fixed-point number format; convert at least a portion of the plurality of data values to the anchored fixed-point number format; perform MAC operations between the converted at least portion and respective weight values, using fixed-point arithmetic, to generate an accumulation value in the anchored fixed-point number format; and determine an output element of a later of a neural network in dependence on the accumulation value.