The authors analyze the problem faced by administration of the Nursing sector of a hospital, in terms of number of personnel. They emphasize that, if estimating formulae are used, these points must be considered: quality of assistance intended, assistance needed by the patients and characteristics of the Institution. Each hospital may use pre-establised formulae, in a first phase, but, depending on the percentage of care requerid by the patients and the general changes that may interfere with the assistance, this calculation must be remade. The purpose of this work, in a modest way, is to provide data, making use of real examples, sothat nurses are able to discuss with the administration or other sectors that may interfere with the Nursing area-about the estimating of the Nursing personel, which is their attribution