Free estimator
Concrete Calculator
Use this concrete calculator to estimate volume, cubic yards, bag quantities, waste allowance, and optional cost for slabs, pads, walkways, and small pours.
Last updated: July 6, 2026
How to measure
Measure the slab length, width, and planned thickness. Use the actual formed dimensions where possible. For irregular areas, divide the pour into smaller rectangles and add the results together.
Formula
cubic feet = length(ft) x width(ft) x thickness(in) / 12
cubic yards = cubic feet / 27
80 lb bags = cubic feet / 0.6
Concrete cost estimate
The optional price field estimates concrete material cost by cubic yard. This is useful for a quick slab budget, but it is not the same as a full delivered ready-mix quote.
Bagged concrete costs are usually easier to compare by bag count. Ready-mix quotes may include delivery, short-load fees, minimum order sizes, fuel surcharges, and local taxes. Confirm those details before buying.
Tips before buying
- Check local requirements for base preparation, reinforcement, and slab thickness.
- Confirm bag yield on the product label before purchasing.
- Plan mixing, placement, screeding, and finishing before concrete starts setting.
- Ask ready-mix suppliers whether delivery, short-load fees, and taxes are included.
FAQ
How much extra concrete should I order?
A 10% waste allowance is a common planning estimate for uneven subgrade, form variation, spills, and small measurement errors.
How many cubic feet does an 80 lb bag of concrete make?
An 80 lb bag is commonly estimated at about 0.6 cubic feet. Always check the bag label for the exact product yield.
When should I order ready-mix instead of bags?
Bagged concrete can work for small projects. Larger slabs may be easier and more consistent with ready-mix delivery.
Does this concrete calculator include delivery cost?
No. The optional cost field estimates material cost by cubic yard only. Ready-mix delivery, short-load fees, tools, reinforcement, base material, and labor are not included.