Free Concrete Volume Calculator with Overdig & Waste Factors

Professional concrete volume calculator for contractors, concrete crews, and DIYers. Calculates cubic yards for slabs, footings, walls, columns, steps, circular pads, and custom shapes. Supports multiple shapes in a single pour.

Unlike basic L×W×D calculators, this tool forces you to account for overdig allowances, pour-specific waste factors, and delivery logistics. It shows you exactly how each adjustment adds yards so you understand why the real number is always higher than the theoretical one.

Conservative by design. Running short mid-pour is catastrophic - a cold joint, an emergency short load at double price, and your crew standing around. An extra half-yard costs $100. The math is obvious.

Pro Tip: Would you rather return half a yard or stop mid-pour and wait 3 hours for an emergency short load at double the price? Always round UP to the next half-yard.

Start Using This Tool See How It Works

How It Works

Select Your Pour Shapes

Choose from 8 shape types: rectangular slabs (with optional thickened edges), circular pads, triangles, footings, walls, columns, steps, or custom area. Add multiple shapes if your pour combines elements like a slab with thickened edges and column pads.
Enter Dimensions

Input length, width, depth, diameter, or whatever the shape requires. The calculator shows an SVG preview with your dimensions labeled. Double-check depth units - entering 6 feet instead of 6 inches will order 12 times too much concrete.
Account for Overdig

Is your subgrade at exact grade? If not, add average overdig depth (typically 0.5-2 inches). The calculator shows exactly how many extra cubic yards this adds. This is the step that separates a $200 mistake from a correct order.
Apply Waste Factor

Waste happens on every pour. The calculator auto-selects waste factors by pour type: 7% for slabs, 12% for footings in dirt, 4% for formed walls. You can override, but it warns you if you go below safe minimums.
Review Your Order

See total volume broken down by base, overdig, and waste. The calculator rounds UP to the next half-yard and gives you a final order number. This is the number you call into the ready-mix plant.
Check Delivery Details

See truck capacity info, short load fee warnings if under 3-4 yards, and an estimated cost breakdown. Plan for extra concrete with practical suggestions.

Built For

Contractors bidding slabs for garages, driveways, patios, and shop floors
Concrete crews sizing pours for commercial foundations and footings
DIY homeowners planning patio slabs, sidewalk sections, and carport pads
Framers calculating footing volumes for decks, pergolas, and post-frame buildings
Masons estimating concrete for retaining wall footings, column bases, and step pours
Pool builders planning shell pours, equipment pads, and decking edges
Agricultural builders sizing pads for equipment sheds, livestock shelters, and grain bins

Features & Capabilities

Overdig Allowance

The feature that separates this from basic calculators. Subgrade is never perfectly flat. Adding 0.5-1 inch average overdig can add 10-20% to your order. The calculator shows you exactly how much in cubic yards so there are no surprises on pour day.

Pour-Specific Waste Factors

Slabs on grade waste less (5-8%) than footings dug in dirt (10-15%). Formed walls waste even less (3-5%). Steps waste more (8-12%) due to complex screeding. The calculator auto-selects based on your shapes and explains the reasoning.

Multi-Shape Combining

Real pours aren't always simple rectangles. Combine a slab with thickened edges, add column pads, throw in a step section. The calculator sums all volumes and applies appropriate waste factors to the combined pour.

Short Load Fee Warning

Most ready-mix plants charge $30-50 per yard for orders under their minimum (typically 3-4 yards). The calculator flags this and shows the estimated fee so you can decide whether to combine pours or round up.

Thickened Edge Support

Garage slabs and building pads often have thickened perimeter edges that act as integral footings. Specify the edge width and extra depth to include this volume automatically instead of calculating it separately.

Visual Shape Previews

Each shape displays an SVG preview with your dimensions labeled. Helps you verify you entered the right numbers before committing to an expensive concrete order. Catches the classic "6 feet instead of 6 inches" mistake.

Comparison

Pour Type	Waste Factor	Common Overdig	Why Waste Occurs
Slab on grade	5-8%	0.5-1"	Minor spillage, screeding waste, form bulge
Footing in dirt	10-15%	1-2"	Soil fallback, uneven trench, no tight forms
Formed wall	3-5%	Rare	Tight forms contain concrete; minor bulge only
Column / Pier	5-8%	Moderate	Small volume, high surface area, overfill risk
Steps / Stairs	8-12%	Moderate	Complex screeding, triangular waste, riser overfill

Frequently Asked Questions

Because it accounts for reality. Most online calculators give you the theoretical "perfect world" volume: length × width × depth. This one adds overdig (your subgrade is never perfectly flat) and waste (every pour spills, bulges, and screed-wastes concrete). Running short mid-pour costs you hours of delay and emergency fees. An extra half-yard costs about $100.

Have a plan. Pour a small stepping stone, fill Sonotube forms for future fence posts, build a tool rest or wheel chock. Some plants accept returns for a fee. An extra wheelbarrow of concrete is vastly preferable to a cold joint and a 3-hour delay waiting for a short load.

It depends on how well you know your subgrade. Machine-graded sites are typically 0.5-1 inch over. Hand-dug footing trenches in loose soil can be 2+ inches over in spots. Walk your site and eyeball low spots before entering a number. When in doubt, round up.

When the mixer truck can't back up within about 150 feet of your pour, or when fences, landscaping, or elevation changes block access. Pump trucks cost $400-800 depending on your area and boom length. Know your site access before pour day.

A short load is any order under the plant's minimum, usually 3-4 cubic yards. Plants charge a premium ($30-50/yard extra) because the truck, driver, fuel, and batch time cost the same whether they deliver 2 yards or 10. If you're near the minimum, consider rounding up to avoid the fee.

Yes. The volume calculation is identical regardless of finish type. Stamped and colored pours are actually less forgiving of shortage because color-matching a patch pour is extremely difficult. Use conservative waste factors and round up aggressively for decorative concrete.

An 80-lb bag of premix yields approximately 0.6 cubic feet, or about 0.022 cubic yards. For a small project like a single fence post hole or a small pad under 0.5 cubic yards, bagged concrete works. For anything larger, ready-mix is dramatically more cost-effective and produces better quality concrete. A 4x4 foot pad at 4 inches thick is about 0.2 cubic yards - roughly 9 bags. A 10x10 foot slab at 4 inches is 1.2 cubic yards - about 55 bags, which takes hours to mix by hand. At that point, call the ready-mix plant.

Standard residential garage slabs are 4 inches thick with thickened edges (12-16 inches deep, 12 inches wide) around the perimeter that act as integral footings. For heavy vehicles, lifts, or heavy equipment, go to 5-6 inches. The thickened edge is the part most people forget to account for in their volume calculation - it can add 15-25% to the total concrete needed. This calculator includes thickened edge support so you get an accurate order quantity.

Disclaimer: This calculator provides conservative volume estimates for planning purposes. Actual concrete needed can vary based on subgrade conditions, form accuracy, and pour technique. Always confirm dimensions on-site before ordering. Concrete cannot be returned once mixed. When in doubt, round up.

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