Though insufficient, increased consumption of healthy diets is necessary to eradicate persistent micronutrient deficiencies and slow rates of diet-related chronic diseases. A new suite of indicators known as the Cost and Affordability of Healthy Diets (CoAHD) uses retail food prices to calculate least-cost diets that meet food-based dietary guidelines, as a measure of physical and economic access to healthy diets. The affordability of least-cost diets helps diagnose issues of food access; where least-cost diets are unaffordable, low availability, high prices, and low incomes are critical barriers to improved diets. Where healthy diets are accessible and still not consumed, preferences and other costs, such as meal preparation, limit dietary improvements. We present evidence on the cost and affordability of healthy diets globally, their relationship to micronutrient adequacy, and how these metrics can inform national policies.