How many weeks does it take for a caterpillar to hatch into a butterfly?

Approximately 3 weeks. Females lay eggs 5 to 7 days after emerging from the chrysalis. The eggs hatch after three days. Caterpillars emerge from the eggs and eat for 10 to 12 days before forming chrysalides. Adult butterflies emerge from the chrysalides in 7 to 10 days.