The equivalent reduction in greenhouse gas emissions (GHGEs) by Mahayana Buddhists with vegetarian diets is quantitatively evaluated. The Buddhists in seven Mahayana-dominated countries or regions, i.e., China, Japan, Vietnam, South Korea, Taiwan, Hong Kong, and Singapore, are studied. Assessments of the vegetarian population among these Mahayana-dominated countries or regions are performed. Correlation formulas based on data from a national survey are developed to quantify the GHGEs of various dietary groups by using the meat consumption as the only required input.