Dorsiflexory wedge osteotomy is indicated for the correction of structural and irreducible first metatarsal deformity to effectively shorten and elevate a plantar flexed first ray. This is most commonly due to fixed forefoot valgus deformity, the cavovarus foot type, and diabetic foot pathologic features involving an ulceration or preulcerative area on the plantar aspect of the first metatarsal head. Surgeons can subjectively judge the amount of correction, such as by restoring the frontal plane alignment of the forefoot, or objectively by returning Meary's angle to a parallel relationship on a weightbearing lateral radiograph. With this tip, we propose an objective measurement, with calculation and use of Meary's angle, to preoperatively quantify the amount of desired correction. In the present study, we applied basic geometric principles based on triangles to calculate the relationship between the width of the excised wedge and the angular degrees of achieved dorsiflexion. We hope these data will provide both objective and reasonable estimates for reconstructive foot and ankle surgeons working with these deformities and with this procedure.