Under 6 months: If you wean before 6 months, baby needs formula as a complete breast milk replacement. Introduce a bottle if baby doesn't already take one. Gradually replace nursing sessions with formula bottles.
6-12 months: Baby is starting solids but still needs breast milk or formula as primary nutrition. Replace nursing sessions with formula bottles and solid food meals. Don't give cow's milk as a primary drink before 12 months.
12-18 months: Whole cow's milk (or appropriate alternative) can replace breast milk nutritionally. Baby should be eating a varied diet of solids. Nursing sessions can be replaced with cups of milk, snacks, and meals. Many families find this age range the easiest for weaning.
18-24+ months: Toddlers nurse more for comfort than nutrition at this point. Weaning is more about changing a comfort habit than about nutrition replacement. "Don't offer, don't refuse" and distraction work well. It's a bigger emotional transition at this age — expect more protest and offer more alternative comfort.
For extended breastfeeding beyond a year, see our extended breastfeeding guide.