How to use the Concrete Cubic Feet Calculator
- Measure the planned pour, including any separate thickened sections. Enter the yield per bag from the chosen concrete product.
- Choose length and width or a known coverage area. Enter depth, allowance and actual package yield; add supplier density or price only when needed.
- Select Calculate. Review the result and its working; if you change an input, calculate again before copying or sharing.
Concrete formula
First calculate the geometric fill volume. Apply the entered percentage allowance to that volume, then divide by product yield and round up to whole bags.
Base volume = area × depth; order volume = base × (1 + allowance ÷ 100); bags = ceil(order volume ÷ bag yield)
What the terms mean
- Length
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Width
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Coverage area
- The measured area to cover, expressed in the selected square unit.
- Fill depth
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Extra volume allowance
- A percentage added to the geometric volume for the planning assumption you choose.
- Actual yield per bag
- Illustrative starting value. Replace with the volume or yield printed on your product.
- Bulk density (optional)
- Enter the supplier’s density for weight. Zero hides the weight estimate.
- Price (optional)
- Price per selected bag, volume unit or US short ton; use one currency consistently.
Concrete worked examples
Estimate bags for a small concrete pad
A 10 ft × 6 ft pad is 3 in deep. Add a 5% volume allowance and use a product that yields 0.45 ft³ per bag.
- Area 60 ft² × depth 0.25 ft = 15 ft³
- Order volume = 15 × (1 + 5 ÷ 100)
- Bags = round up (15.75 ÷ 0.45)
Answer: 15.75 ft³. Base volume: 15 ft³; Cubic yards: 0.583333 yd³; Litres: 445.990334 L; Whole bags: 35 bags.
Order concrete using known coverage area
Cover 100 ft² at a uniform 2 in depth with no allowance. The example product yields 0.45 ft³ per bag; an illustrative bulk price is 10 currency units per yd³.
- Area 100 ft² × depth 0.166667 ft = 16.666667 ft³
- Order volume = 16.666667 × (1 + 0 ÷ 100)
- Bags = round up (16.666667 ÷ 0.45)
Answer: 16.666667 ft³. Base volume: 16.666667 ft³; Cubic yards: 0.617284 yd³; Litres: 471.947443 L; Whole bags: 38 bags; Estimated cost: 6.17284 currency units.
Concrete Cubic Feet Calculator FAQs
Can I use a 60 lb or 80 lb bag?
Use the volume yield printed for that exact mix. Do not calculate yield from the bag weight alone.
Why are bag counts rounded up?
A partial bag cannot supply the full required volume. Bag counts use the order volume including your entered allowance.
Measurement guide for Concrete
Measure the pour area and planned thickness. Calculate thickened edges or footings separately; obtain bag yield from the specific product label.
Assumptions and limits
Bag mass does not establish concrete yield. Mixing, placement and product yield matter; this calculator does not design a structural slab.
Bag yield and bulk density depend on the actual product. Allowance is applied to volume; bags are rounded up.
Check your result
Compare the base volume with area multiplied by depth in feet. The order volume includes your allowance; a bag count is rounded up using the entered product yield.