Concrete Calculator

Concrete Calculator – Volume, Bags & Cost Estimator

Concrete CalculatorFree Tool

Calculate concrete volume in cubic yards, cubic feet and cubic meters for any shape. Get bag count and cost estimates instantly.

Concrete Volume Calculator
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Tip: Add 5 to 10 percent to your order for waste, spillage and uneven subgrade. For difficult pours, use 10 percent.
Concrete Bag Coverage Reference
Bag Size Bags per Cubic Yard Bags per Cubic Foot Coverage per Bag
80 lb bag45 bags1.67 bags0.60 cu ft
60 lb bag60 bags2.22 bags0.45 cu ft
50 lb bag72 bags2.67 bags0.375 cu ft
40 lb bag90 bags3.33 bags0.30 cu ft
Recommended Slab Thickness Guide
Project TypeTypical ThicknessNotes
Sidewalk or walkway4 in (100 mm)Often with light reinforcement
Patio or terrace4 in (100 mm)Use compacted base; 5 in for heavy loads
Driveway (passenger cars)4 to 5 in5 to 6 in for frequent truck traffic
Garage slab4 to 5 inThicken at edges per specs
Hot tub or spa pad6 in (150 mm)Confirm load; add reinforcement
Shed pad4 in (100 mm)Consider thickened edge for heavy sheds
Structural footings8 to 12 in depthAlways confirm local building code

How to Use This Concrete Calculator

This concrete calculator gives you accurate volume estimates for nine common structure types. Select your shape, enter dimensions in your preferred units and click Calculate to see results in cubic yards, cubic feet and cubic meters instantly.

Step by Step Guide

  1. Choose the shape of your concrete structure using the tabs at the top of the calculator.
  2. Enter each dimension using either US units (inches, feet) or metric units (centimeters, meters).
  3. Enter the number of identical units if you have more than one (for example, 12 fence post holes).
  4. Optionally enter a price per cubic yard, cubic foot or cubic meter to estimate total project cost.
  5. Press Calculate or hit Enter to view results.
Pro tip: For irregular shapes, break the area into simple rectangles or circles, calculate each one separately, and add the totals together.

Concrete Volume Formulas Explained

Concrete volume formulas are straightforward once you know the shape. All formulas below use measurements converted to feet before calculating.

Square Slab, Footer, Wall and Column

Volume (ft³) = Length (ft) × Width (ft) × Depth or Height (ft)
Volume (yd³) = Volume (ft³) ÷ 27
Volume (m³) = Volume (ft³) × 0.0283

Round Slab and Round Column

Area (ft²) = π × (Diameter ÷ 2)²
Volume (ft³) = Area × Depth or Height
Volume (yd³) = Volume (ft³) ÷ 27

Tube (Hollow Round)

Outer Area (ft²) = π × (Outer Diameter ÷ 2)²
Inner Area (ft²) = π × (Inner Diameter ÷ 2)²
Volume (ft³) = Height × (Outer Area − Inner Area)

Steps

Volume below platform (ft³) = Platform Depth × (Rise × Steps) × Width
Volume below each step (ft³) = Run × (Rise × Step Number) × Width
Total = Sum of all section volumes

Curb and Gutter

Curb Volume (ft³) = Curb Depth × (Curb Height + Flag Thickness) × Length
Gutter Volume (ft³) = Gutter Width × Flag Thickness × Length
Total = Curb Volume + Gutter Volume

What Is Concrete and How Is It Made

Concrete is one of the most used construction materials in the world. Understanding its composition helps you choose the right mix for your project.

Concrete is a composite material made by combining cement (the binder), water, sand (fine aggregate) and gravel or crushed stone (coarse aggregate). When water contacts cement, a chemical reaction called hydration begins. This process binds the aggregates into a dense, rock-like mass that gains strength over time.

Cement vs Concrete

Cement is just one ingredient. Concrete is the finished product. A common mix ratio for general construction is 1 part cement to 2 parts sand to 3 parts gravel by volume, plus enough water to make it workable.

Common Concrete Applications

Concrete is used across residential, commercial and civil construction. Common applications include patios, driveways, sidewalks, garage slabs, footings, retaining walls, columns, steps, curbs, gutters and parking lots. It is also used for fence and deck post holes, equipment pads and drainage channels.

Tips for Accurate Concrete Estimates

Accurate concrete estimates save money and prevent costly project delays. Follow these planning tips before placing your order.

Account for Waste and Overage

Always order 5 to 10 percent more than your calculated volume. Concrete is lost to spillage, slightly uneven subgrade, over-excavation and form variance. For complex forms or first-time pours, use 10 percent overage.

Keep Units Consistent

Mix errors are the most common source of calculator mistakes. Decide whether you are working in US units (inches and feet) or metric units (centimeters and meters) and stay consistent across all inputs. This calculator handles unit conversion automatically when you select your unit for each field.

Sloped Slabs Use Average Depth

For slabs that slope or taper, calculate the average thickness by adding the minimum depth and maximum depth, then dividing by two. Use that average as your depth input.

Reinforcement Does Not Change Volume

Adding rebar, wire mesh or fiber reinforcement does not meaningfully change the volume of concrete required. Calculate volume based on the form dimensions only, then plan reinforcement separately based on structural requirements.

Frequently Asked Questions

How do I calculate how much concrete I need?+
Multiply length by width by depth, all measured in feet, to get cubic feet. Then divide by 27 to convert to cubic yards. For example, a slab 10 ft long, 10 ft wide and 4 inches (0.333 ft) deep requires 10 × 10 × 0.333 = 33.3 cubic feet, which equals about 1.23 cubic yards. Use this calculator above to handle the conversion for you automatically.
How many bags of concrete equal one cubic yard?+
You need approximately 45 bags of 80-lb concrete, 60 bags of 60-lb concrete, or 90 bags of 40-lb concrete to fill one cubic yard. These are approximate values. Always check the yield printed on the bag because it varies slightly by brand and mix design.
How much does a cubic yard of concrete weigh?+
A cubic yard of concrete typically weighs between 3,700 and 4,100 pounds, which is roughly 2 tons. The exact weight depends on the specific mix design, aggregate type and moisture content at the time of delivery.
How much extra concrete should I order?+
Order 5 to 10 percent more than your calculated volume. This accounts for waste, spillage, slight over-excavation and variance in form dimensions. For complex or irregular pours, round up to 10 percent. Running short mid-pour is far more disruptive than having a small amount left over.
How long does concrete take to cure fully?+
Concrete is generally safe to walk on after 24 to 48 hours. It can support vehicle traffic after about 7 days. Full design strength is reached at 28 days. Curing speed depends on temperature, humidity, mix design and whether curing compounds or covers are used.
What thickness should a concrete slab be?+
Most residential slabs, driveways, sidewalks and patios use 4 inches of thickness. Garage slabs and areas with frequent heavy vehicles typically need 5 to 6 inches. Hot tub pads and structural footings often require 6 inches or more. Always follow local building codes and engineering specifications for your specific project.
What is the difference between cement and concrete?+
Cement is the binding agent used to make concrete. Concrete is the finished building material, which is a blend of cement, water, sand and gravel. You pour concrete; cement is just one ingredient inside it. When people say “cement slab,” they almost always mean a concrete slab.
Should I use bagged concrete or ready-mix?+
Use bagged concrete for small projects under about 1 cubic yard. Mixing bags yourself lets you work at your own pace and is cost-effective for small jobs. Ready-mix concrete delivered by truck is better for larger pours because it is consistent, saves labor and arrives pre-mixed. Ready-mix requires scheduling a delivery window and completing the pour quickly before the concrete begins to set.
What temperature is best for pouring concrete?+
The ideal temperature range for pouring concrete is 50 to 70 degrees Fahrenheit (10 to 21 degrees Celsius). Cold temperatures slow curing and can cause freezing damage before the concrete sets. Hot temperatures speed up set time and can cause premature cracking. Follow supplier guidance and use proper curing methods such as curing blankets in cold weather or wet burlap in heat.