Concrete Calculator
Cubic yards, bagged mix and cost for slabs, footings and columns.
How it works
For a rectangular pour, cubic feet equal length × width × depth in feet. A round column uses π × radius² × height. The allowance is applied before cubic feet are divided by 27 to produce cubic yards.
Bag count comes from finished yield, not bag weight alone. The presets follow common 40/50/60/80 lb concrete-mix yields, but the field stays editable so the selected product data sheet controls the order. Ready-mix pricing excludes delivery, short-load fees, taxes and supplier rounding.
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How the Concrete Calculator works
This US concrete calculator estimates cubic feet, cubic yards and bagged concrete for slabs, rectangular footings and round columns. It keeps the allowance, bag yield and both bagged-mix and ready-mix prices visible instead of hiding them in one rounded answer.
Choose the geometry that matches the form
A slab or rectangular footing is length × width × depth. Enter length and width in feet and average depth in inches; the calculator converts depth to feet before multiplying. A round column uses π × radius² × height, with diameter entered in inches.
Count multiplies identical pours. For a continuous strip footing, use its total run as length and keep count at one. Irregular projects should be split into rectangular or round sections and added rather than forced into one average rectangle.
Cubic yards and bags answer different purchase questions
Ready-mix concrete is quoted in cubic yards, so the allowance-adjusted cubic feet are divided by 27. The material-price result is cubic yards × price and deliberately excludes delivery, taxes, supplier rounding and short-load or minimum-order charges.
Bagged concrete is counted from finished yield. QUIKRETE publishes approximate yields of 0.30, 0.375, 0.45 and 0.60 ft³ for 40, 50, 60 and 80 lb Concrete Mix bags. Those are presets, not universal guarantees: replace the yield with the selected product data sheet before ordering.
Why the allowance stays visible
Forms leak, subgrade depth varies and some concrete remains in the mixer, wheelbarrow and tools. Ten percent is a common planning allowance for a prepared slab, but a measured, level form can need less and uneven excavation can need more.
Do not add water to stretch a short batch. Water content affects strength and durability. When the required volume is too large to place continuously with the available crew and mixer, compare ready-mix logistics rather than only the material price.
FAQ
How much concrete is needed for a 10 × 6 ft slab 4 in thick? expand_more
The net volume is 20 ft³. With a 10% allowance it becomes 22 ft³, or about 0.81 yd³. At 0.60 ft³ per 80 lb bag, round up to 37 bags.
How many 80 lb bags make one cubic yard? expand_more
At an approximate 0.60 ft³ yield, one 27 ft³ cubic yard takes 45 bags before any allowance. Product yield and jobsite loss can move the actual order.
Does the ready-mix cost include delivery? expand_more
No. It is only cubic yards times the entered material price. Add the supplier's delivery, short-load or minimum-order fee, taxes and any rounding rule to compare a real quote.