Behind the result
Simple formula. Clear assumptions.
Volume = length × width × thickness
Order estimate = volume × (1 + extra % ÷ 100)
All dimensions are converted into consistent units before calculating. One cubic yard equals 27 cubic feet. One foot equals exactly 0.3048 metres. Results are rounded for display, not during calculation.
This tool assumes a uniform rectangular slab. It does not determine safe slab thickness, reinforcement, foundations, or compliance with building codes.
Worked example
A 10 × 10 ft slab, 4 inches thick
10 × 10 × (4 ÷ 12) = 33.333 cubic feet.
Divide by 27 to get 1.235 cubic yards.
Add 10% extra to get approximately 1.358 cubic yards.
The 10% default is an editable planning assumption, not a universal recommendation. Site conditions and supplier order increments may change what you need to order.
USD/CAD changes the cost label only. It does not convert exchange rates. Bag estimates will be added later using manufacturer-stated yield.