rough guess

The cave was about twenty feet across, at a rough guess, and something more than half that deep.

"From that and the flies, I'd give a rough guess of four to twelve hours."

A rough guess is that more than 400 students is too big.

At the side put down a rough guess of the cost that might be involved.

He could make a rough guess at a storage depot.

You wouldn't have let her off the hook without taking a rough guess.

"I'll have to check with shipping, but at a rough guess I would say between 150 and 200."

The amount of power in the heat ray-a rough guess.

Its extent was, at a rough guess, a hundred acres.

Next I gave the ship a rough guess for the planet's rotation rate.