Concrete Calculator

How do I measure a slab, footing, column, wall, or steps?

Measure the outside sizes you already plan to build, in feet and inches. A 4 inch thickness appears in the worked example below. It is not a recommended slab thickness. Footings use depth. Columns and piers use height. Solid steps use width, total run, and total rise.

Inches can be 6, 3.5, 1/2, or 3 1/2. Eighteen inches is read as 1 foot 6 inches. Each side must be greater than zero and no more than 10,000 feet. Type the thickness or depth you already plan to use. This page does not choose a thickness, a concrete strength, or a size that meets a building code.

What does the 10 by 12 foot slab example come to?

A 10 foot by 12 foot slab at 4 inches thick, with 5% added once, is 42 cubic feet, or 1.5556 cubic yards.

Slab, 10 ft by 12 ft by 4 in, with a 5% allowance

1. Four inches is 4 ÷ 12 = 1/3 foot. That thickness is one you chose.
2. Base volume, before any allowance, is 10 × 12 × 1/3 = 40 cubic feet. That is 40 ÷ 27 = 1.4815 cubic yards on screen.
3. The 5% allowance is added once: 40 × 1.05 = 42 cubic feet, or 1.5556 cubic yards. That is the volume with allowance.
4. An 80 lb QUIKRETE Concrete Mix bag is about 0.60 cubic feet of premixed concrete. 42 ÷ 0.60 = 70 whole bags. At $7 a bag, the bag cost is $490. The bag count uses 42 cubic feet, not the rounded yard order below.
5. A supplier increment of 0.25 cubic yards rounds 1.5556 up to a nominal order of 1.75 yd³. At $150 per cubic yard, the material cost is 1.75 × 150 = $262.50.
6. Delivery of $50 stays separate. The combined total is $262.50 + $50 = $312.50.
7. The unrounded material estimate, before delivery, is (42 ÷ 27) × 150 = $233.33. It is a comparison, not the purchasing total.

The button below fills those entries, opens the optional prices, and calculates. Change any number afterward, or choose Reset.

Round column, 2 ft diameter by 8 ft tall

The radius is half the diameter: 2 ÷ 2 = 1 foot. Base volume is pi × 1 × 1 × 8 = 25.1327 cubic feet on the screen. That number has no allowance in it. Add one yourself if you want extra. This is the concrete inside the column, not a footing under it.

Solid-filled steps, 3 ft wide, 4 ft total run, 2 ft total rise, 4 steps

Four equal steps means each tread is 4 ÷ 4 = 1 foot and each riser is 2 ÷ 4 = 0.5 foot. Because the stair is solid filled, the side area adds the concrete under every tread: 1 × 0.5 × (1 + 2 + 3 + 4) = 5 square feet. Times the 3 foot width, the base volume is 15 cubic feet.

The space under the treads is concrete. This is not a hollow stair, a wood stair with separate boards, or a stair with open risers. Those need a different measurement. If the steps are not equal, this description does not fit.

How do the cubic yard formulas work?

Turn every side into feet, multiply the shape, then divide cubic feet by 27 to get cubic yards. The allowance is applied once after that.

• Slab or patio: length × width × thickness.
• Footing: length × width × depth.
• Round column: pi × (diameter ÷ 2)² × height.
• Rectangular column: length × width × height.
• Wall: length × height × thickness.
• Solid steps: width × total run × total rise × (step count + 1) ÷ (2 × step count).

• 1 cubic yard = 27 cubic feet. Prices are in US dollars.
• 1 cubic foot is about 7.48 US gallons. The results use 7.48051948. Gallons only restate the base volume. They are not an amount to order.
• Volume with allowance = base volume × (1 + allowance ÷ 100). The allowance is added once.
• Nominal order = that volume in cubic yards. If you enter a supplier increment, it rounds up to that step. It is not a promise a supplier will deliver it.
• Material cost = nominal order × your price per cubic yard. A blank price stays unknown. Zero is $0.
• Unrounded material estimate = volume with allowance, in cubic yards, × the same price, before delivery.
• Combined total = material cost + delivery, only when both are entered.
• Whole bags = cubic feet with allowance ÷ the selected bag yield, rounded up. Bag cost = whole bags × your price per bag.

Volumes on screen show 4 decimal places. Dollars show cents. The math stays more exact until an order or a whole bag has to be decided.

What do people ask about cubic yards and bags?

Should I order ready-mix or bags of concrete?

Order ready-mix when you want cubic yards delivered. Order bags when the job is small enough to mix by hand or in a portable mixer. The volume is the same either way. One cubic yard is 27 cubic feet.

A ready-mix plant will ask for a strength, often a specified compressive strength in pounds per square inch (psi), plus details such as slump. This page does not choose a psi, a strength class, or a mix. If you want a dollar figure, type the price you were quoted.

Bag counts on this page use 40, 50, 60, and 80 lb bags of QUIKRETE Concrete Mix, product 1101. Those are premixed concrete, cement and aggregate together, not bags of cement only. The 90 lb size on that product sheet is not calculated here. Read the bag you buy, because another brand can list a different yield.

The waste allowance starts at 5% and is added once. It is a spare you choose for spillage, uneven subgrade, or forms that run a little large. It is not a measured waste total for your job. Rebar and wire mesh are not subtracted from the volume, and this page does not design them. If this volume already includes the allowance, do not add that same percent again on the concrete materials calculator.

Which calculator matches what you are buying?

Use the page that matches the material. This page is only the poured volume.

• Concrete block calculator for a CMU wall count, using a nominal face such as 16 by 8 inches with the mortar joint included.
• Concrete weight calculator for pounds and US short tons from a volume and a density in pounds per cubic foot.
• Concrete materials calculator for loose cement, sand, and gravel from a mix ratio you type.

Where are the notes for the whole site?

Notes that apply to the whole preview, not just this volume calculator, are on separate pages: About, Contact, Privacy, and Disclaimer. The public email is on the Contact page.

What does this calculator refuse to decide?

It estimates quantity only. Thickness, strength, reinforcement, and code checks stay with you or a qualified professional.

• Results are quantity estimates from the formulas on this page. They are not a design for the structure, a recipe for the mix, or a building-code check.
• The page does not choose a slab thickness, a concrete strength, or which bag to buy.
• The allowance is a percent you choose, from 0 to 20. It is not a measured waste amount for a particular job.
• The nominal order is not a promise that a plant will deliver that fraction of a yard or have a truck available.
• Bag yields are approximate published yields for one premixed product. They are not universal.
• The stair formula is only the solid-filled stair with equal steps.
• Each measurement is limited to 10,000 feet. Step count is limited to 1,000. Prices and delivery are limited to $1,000,000. A supplier increment must be from 0.01 to 1,000 cubic yards. Values that cannot produce a finite result are rejected.
• Feet, inches, cubic feet, cubic yards, and US dollars are the measures used here. Gallons only restate the base volume.

The disclaimer covers the same limit for all four calculators.