Numeracy skills are essential if children are to succeed academically. We investigated the efficacy of short fl uency-building exercises to target a number of essential numeracy skills (writing digits and simple addition problems). We further wanted to ascertain whether such an intervention would impact their ability to solve related but unpractised subtraction problems. Children from two mainstream primary schools (aged 9–10) were allocated randomly to either a uency-building intervention group (FBI; n = 19) or a control group (C; n = 10). The intervention group engaged in daily uency-building practice that consisted of writing and reciting essential numeracy facts. The control group children received their standard instruction. The study took place over ve weeks; following the intervention, the children in the FBI group performed signi cantly better (p < .05) on three of the four numeracy elements with large e ect sizes (d = 1.25–1.67). Results are discussed in the context of incorporating simple essential skills uency-building exercises into mainstream classes, and how the implementation need not be costly in terms of sta time or resources.