Basic concrete slab cost. I'll base my price on what my actual estimate would be to install a 6 thick concrete slab for one of my customers. Base cost for a 6 thick concrete slab -- $4.00 dollars per square foot --. Take the length of the concrete slab x the width of the slab to get the. total square footage. Multiply the total square footage by 4 (dollars) to get the total price.