How to measure concrete
Measure the finished dimensions of the concrete shape. Slab thickness and footing depth are entered in inches for US units or centimeters for metric units.
Method
Slab volume = length x width x thickness
Wall volume = length x height x thickness
Footing volume = length x width x depth
Round form volume = pi x (diameter / 2)^2 x height or thickness
Wall volume = length x height x thickness
Footing volume = length x width x depth
Round form volume = pi x (diameter / 2)^2 x height or thickness
Bag yield constants
This calculator uses QUIKRETE concrete mix planning yields: 40-lb bags at 0.3 cubic feet, 60-lb bags at 0.45 cubic feet, and 80-lb bags at 0.6 cubic feet.
Assumptions
- Bag counts and ready-mix volume include the entered waste allowance.
- Ready-mix cost is calculated from waste-adjusted cubic yards.
- Excavation overdig, forms, reinforcement, vapor barrier, base gravel, and finishing supplies are separate.
- Structural work can require engineered design and inspections.
FAQs
Should I use bags or ready-mix concrete?
Small repairs and post footings are often practical with bags. Larger slabs are usually easier to plan as ready-mix cubic yards.
Why do bag counts look high?
Bags yield a small finished volume. The calculator rounds each bag size up separately so you can compare purchase options.
Does this design the slab or footing?
No. Reinforcement, subbase, frost depth, drainage, soil bearing, and local code are outside this quantity estimate.
Reference
Bag yield values are based on the QUIKRETE concrete mix data sheet.