How to Tell When a Pot Is Simmering

At a simmer, small bubbles rise and break in a few places while most of the surface stays calm. At a rolling boil, large bubbles churn almost the entire surface continuously. When a recipe says to bring the liquid to a boil and then lower the heat, aim for the gentler pattern.

When to turn down the heat

Once the liquid boils, turn down the burner and watch the surface for a few seconds. The pot can retain heat for a while. If large bubbles keep breaking, lower the heat a little more. If the surface goes still, raise the heat in small increments until small bubbles return.

Soup and pasta call for different movement

A simmer cooks soup without tossing the ingredients around the pot. A stronger boil is suitable for pasta water. Adding a cold ingredient can pause the bubbling temporarily. Give the liquid a moment to recover before adjusting the burner again.

Common questions

Does steam alone mean it is simmering?

Look for small bubbles actually reaching and breaking on the surface. Steam alone, or bubbles clinging to the bottom, gives less information about how the liquid is moving.

Should I keep the lid off?

Follow the recipe’s instructions for the lid. After covering the pot, you may need to adjust the heat again. Lift the lid briefly to check the surface.

Look for this bubbling pattern during the low-heat step of this red lentil soup recipe.

For the appearance of the bubbles, see University of California Cooperative Extension’s guide.