The length of the oral calculation card in the third grade of primary school can be different according to the actual situation. Usually, the length of the oral calculation card is about 20-30 cm, that is, 200-300 mm This length range can accommodate enough oral calculation questions, but it is not too long or too short, which is convenient for students to use. However, whether the length of the specific oral calculation question card meets this range still needs to refer to the actual teaching materials or school regulations. If there are specific textbooks or school regulations, it is recommended to refer to relevant textbooks or consult school teachers to obtain the exact length.