I think you are confused. You cannot have a coverage of more than 100%. This sort of figure is usually quoted when coverage is estimated using (highly inaccurate) indirect methods which confuse prevalence for incidence. The fact that > 80% of GAM cases are aged between 6 and 23 months does not mean that the prevalence of GAM in this in this age-group is 80%. You need to have the prevalence. SMART type surveys usually provide age-specific prevalence estimates for this age-group. Anyway ... The standard approach to your problem is to apply the formula: case load = N * P * K * C where: N is the size of the population in the program area. An appropriate value for N is usually derived from census data. P is estimated prevalence. This is usually estimated using a nutritional anthropometry survey (e.g. a SMART survey). It is important that prevalence is estimated for the program's admitting case-definition. K is a correction factor to account for new (incident cases) over a given time period. This is usually taken to be 2.6 over one year. C is the expected mean program coverage over a given time period. You have an indirect estimate but this is a clear overestimate. You could correct what you have by divining by K (above). If you have an indirect estimate of coverage of 120% then you might use: C = 120 / 2.6 = 46% = 0.46 (as a proportion) If we assume: Population (N) = 10,501 Prevalence (P) = 8.7% = 0.087 (as a proportion) Correction (K) = 2.6 Expected coverage (C) = 46% = 0.46 (as a proportion) We get a one-year case-load of: case load = N * P * K * C case load = 10501 * 0.087 * 2.6 * 0.46 case-load = 1093 You can use the 95% CI on P to get a nominal 95% CI on the case-load. I hope this is of some use. The material presented in response is based on: Garenne M, Willie D, Maire B, Fontaine O, Eeckels R, Briend A, Van den Broeck J, Incidence and duration of severe wasting in two African populations, Public Health Nutr. 2009 Nov;12(11):1974-82 Anon, WHO, UNICEF, WFP and UNHCR Consultation on the Programmatic Aspects of the Management of Moderate Acute Malnutrition in Children under five years of age 24-26 February 2010, WHO, Geneva, 2010 MacMahon B, Pugh TF, Epidemiology Principles and Methods, Little Brown & Company, Boston, USA, 1970 Miettinen O, Estimability and estimation in case-referent studies, American Journal of Epidemiology, 1976;103(2):226–235