GUIDE · 2026-07-23
How to use the Concrete Calculator
U.S. slabs are commonly measured in feet for plan dimensions and inches for depth. The calculator converts depth to feet, computes volume and divides by the cured yield printed on each bag.
How it works
Volume (ft³) = length (ft)×width (ft)×depth (in)÷12
Most processing stays in your browser instead of sending inputs to our server. Verify important financial or contractual decisions against an authoritative source.
Step-by-step
- 01Enter slab length and width in feet and depth in inches.
- 02Set an allowance, the bag's ft³ yield and optional bag price.
- 03Review ft³, yd³ and m³ volume plus the rounded whole-bag order.
Worked example
INPUT10×4 ft; 4 in deep; 10% allowance; 0.6 ft³ bag yield
RESULTAbout 14.67 ft³ to order → 25 bags
Use the product's stated yield, not bag weight alone.Limits and checks
- This does not design a structural slab or specify reinforcement and base preparation.
- Irregular geometry, compaction and site loss require separate judgment.
Useful examples
- Size a walkway slab
- Estimate 80 lb premix bags
- Compare bagged mix with a ready-mix quote
Frequently asked questions
Where do I find bag yield?
Use the cured-volume yield in cubic feet printed on the product bag. Bag weight alone does not determine yield.
How are cubic yards calculated?
The cubic-foot order volume is divided by 27.
Can this design a structural foundation?
No. It estimates material only; follow drawings, codes and qualified guidance for depth, reinforcement, soil and mix design.