Dad’s short answer: Two to six hours for a well-extracted carpet in a room with airflow. If it's still damp the next morning, you used too much water, didn't make enough dry passes, or the room has no air moving through it.

How to cut the drying time

Dry passes are the biggest lever. After the wet passes, go back over the same area with the solution off, pulling suction only, until the machine stops picking water up. Most people stop two or three passes too early, and that's the whole difference between a few hours and overnight.

Use less solution. More water in means more water to get out, and it doesn't clean better.

Move air. Open windows, run ceiling fans, put a box fan at floor level pointed across the carpet. A dehumidifier helps a lot in a humid house.

Don't put furniture back until it's dry, and put foil or plastic under the legs if you have to — wood and metal feet can stain damp carpet.

Why it matters beyond convenience

Carpet that stays wet too long is a mildew risk, and the smell that develops in the backing and pad is far harder to remove than whatever you were cleaning in the first place. Twenty-four hours damp is the point where I'd start worrying.

Damp carpet also attracts dirt fast. Walking on it before it's dry drives fresh soil straight into the fibers you just cleaned, which is why the room can look worse two days later.

So the honest advice is to clean when you can leave the room alone for the rest of the day. Morning is better than evening for exactly that reason.

Dad’s Take: More dry passes, less water, and move some air. Do all three and you'll walk on it the same evening.