hi there, i don't happen to have that exact amount handy as the homeowner took care of filling those/that part of the project. Generally we line the base with about 1/3 lava rock (light and porous) then the rest with composted soil amender with a liner of landscape fabric in between the layers. here is a site that often can calculate soil quants for you depending upon the size of the tub/vessel: http://www.gardeners.com/how-to/soil-calculator/7558.html