The length of time required to boil lentils can vary depending on the type and age of the lentils. Here are some general guidelines:

  1. Red Lentils: Red lentils typically cook faster than other types of lentils and can be ready in as little as 15-20 minutes of boiling.

  2. Green/Brown Lentils: Green or brown lentils usually take around 30-40 minutes to cook. Soak them in water for at least an hour before boiling to reduce the cooking time.

  3. French Lentils: French lentils are smaller in size and tend to hold their shape well when cooked. They take approximately 25-30 minutes to boil.

  4. Black Lentils: Black lentils, also known as beluga lentils, require around 20-30 minutes of boiling.

Regardless of the type, it's essential to rinse the lentils thoroughly before cooking and add enough water or broth to cover the lentils by about an inch or two. You can also add seasonings such as salt, bay leaves, and garlic to enhance the flavor of your lentils.