HOW MUCH DO YOU NEED?
One ounce of pebbles equals about 1 square inch.
For a patio that is 4" x 2" --> 4 x 2 = 8 square inches. So you will need 8 ounces or 1/2 lb of pebbles. This is for a 1" deep patio so if you don't need it that deep, it will go a bit farther.
*Not a toy, not meant for young children.