Concrete Calculator FAQ

Multiply length × width × thickness in feet, then divide by 27 to get cubic yards. See the formula, a size chart, and how much waste to add.

Length (ft) × width (ft) × thickness (ft) ÷ 27 = cubic yards of concrete. Worked examples for slabs, footings, post holes, and round columns.

A 4-inch slab needs about 1.23 cubic yards per 100 square feet. Use the chart to find the yardage for common slab sizes, or run your own numbers.

Divide your total cubic feet by the bag yield: 0.6 for an 80 lb bag, 0.45 for a 60 lb bag. See the full chart and worked examples for slabs and posts.

It takes 45 bags of 80 lb concrete mix to make one cubic yard, or 60 bags of 60 lb mix. Full chart for 40, 50, 60, 80, and 90 lb bags.

An 80 lb bag of concrete mix yields about 0.6 cubic feet. A 60 lb bag yields 0.45 and a 40 lb bag yields 0.3. See yields for every common bag size.

A 10x10 slab at 4 inches thick needs 56 bags of 80 lb concrete mix, or 75 bags of 60 lb mix. See counts for 4, 5, and 6 inch thicknesses.

Most 4x4 fence posts take 2 to 3 bags of 60 lb concrete per hole, or 2 bags of 80 lb. See the chart by hole diameter and depth, plus the formula for any size.

A pallet of 80 lb concrete mix holds 42 bags, about 3,360 lb and 25.2 cubic feet. See pallet counts and weights for 40, 50, 60, and 80 lb bags.

Ready-mix concrete runs about $140 to $200 per cubic yard delivered in 2026, before short-load fees. See what drives the price and how to budget a small pour.

A cubic yard of concrete is 27 cubic feet, covers 81 square feet at 4 inches, weighs about 4,050 lb, and costs roughly $140 to $200 delivered.

A poured concrete slab costs about $6 to $12 per square foot installed in 2026, averaging around $8. See costs by slab size and what DIY saves.

A standard ready-mix truck holds 8 to 11 cubic yards, and most deliver 9 to 10 because of road weight limits. See capacities and what a full load weighs.

A full 10 yard truck of concrete costs roughly $1,400 to $2,000 delivered in 2026. See the price breakdown, delivery fees, and cost per square foot.

A cubic yard of concrete weighs about 4,050 lb, or roughly 2 tons, at a standard density of 150 lb per cubic foot. See wet vs cured and metric weights.

A cubic foot of normal-weight concrete weighs about 150 lb, or 145 lb without reinforcement. See weights by slab thickness and mix type.

Four inches is standard for patios, walkways, and shed pads. Driveways need 5 to 6 inches, and anything carrying trucks or RVs needs 6 inches or more.

Multiply length by width and depth in feet. Divide cubic feet by 27. Use the examples for rectangles, circles, and areas that are not level.

One cubic yard of dirt does not have a constant weight. Use the material density and water condition to calculate the load weight.

One cubic yard of loose, dry gravel weighs approximately 2,730 lb, or 1.37 US tons. Moisture, grading, and compaction change the weight.

Use $10 to $50 as an initial price for one US ton of common bulk gravel before tax and delivery. Product type and local delivery can change the price.

One cubic yard covers 324 square feet at a depth of 1 inch. Use the coverage table for depths from 1 to 12 inches.

More dirt is necessary when compaction decreases the specified volume. Use the formula and table to calculate the loose quantity.

Use fill dirt to change the grade or fill a deep area. Use topsoil for grass, gardens, and other plant areas.

Compare the dirt weight with the pickup payload limit. Use the vehicle label and supplier weight before you load the truck.

The fence height, soil, frost depth, and local requirements can change the specified depth. Calculate the depth and the necessary post length.

Many wood fences use a maximum post spacing of 8 ft. Use the product specification and calculate each fence run separately.

Calculate the hole volume and subtract the post volume below ground. A 12 in hole that is 30 in deep uses approximately 1.75 ft³ around a 3.5 in post.

Divide the concrete volume for one hole by the yield on the concrete bag. Use the next whole-bag quantity.

Add one gap to each fence run. Divide by the picket width plus the gap. Use the next whole-picket quantity.

Divide each fence run by the maximum post spacing. Use the next whole-section quantity. Then, add the end posts, corner posts, and gate posts.

Divide the rise by the run. Multiply by 12 for rise per 12. Calculate the inverse tangent to get the roof angle.

Calculate the square root of the run squared plus the rise squared. Add the sloped tail length for the overhang.

A 4/12 roof pitch has an angle of 18.43 degrees. The rafter multiplier is 1.0541 for each horizontal run unit.

The permitted spacing depends on lumber size, species, grade, span, loads, and local requirements. Use the approved plans or a span table.

Use the roof pitch and the specified seat length. Calculate the heel depth. Compare the remaining rafter depth with the plans.

Divide the roof length by the maximum spacing. Increase a partial result to the next whole space. Add one rafter position.