The Concrete Slab Calculator Built Into Every Metal Building Quote
SimpleLexi's concrete slab calculator sizes the pad, calculates cubic yards, and estimates cost for every building your customers design, so your quotes include the foundation, not just the steel. Free for dealers.
What Is the SimpleLexi Concrete Slab Calculator?
The SimpleLexi Concrete Slab Calculator is a built-in tool in the free SimpleLexi 3D configurator. When a customer designs a carport, garage, or workshop, the calculator reads the building's footprint, recommends a slab size and thickness, calculates the cubic yards of concrete required, and adds an estimated cost to the quote.
Rebar, vapor barrier, and thickened edges are priced in with one tap. The customer sees the full project cost before they order, and you stop fielding the "so what about the slab?" call after the deposit clears. The calculator runs inside the carport builder and the garage designer, on SimpleLexi.com and in the widget on your own site.
- Slab size taken automatically from the building footprint
- Cubic yards and estimated cost on the same quote as the steel
- Rebar, vapor barrier, and thickened-edge add-ons
- Pairs with permit requirements by zip code
How the Concrete Slab Calculator Works
The customer never types a dimension twice. The building they designed is the slab they get quoted.
Customer Designs the Building
They pick a standard build and customize it in 3D. The calculator watches the width and length as they change.
The Calculator Sizes the Slab
It matches the slab to the building footprint and recommends a thickness for the building type: 4 inches for carports and garages, more for workshops and RV buildings.
It Calculates Cubic Yards
Length times width times thickness, converted to cubic yards, with a waste factor so the customer orders enough concrete the first time.
It Adds the Estimate to the Quote
An estimated slab cost, plus any add-ons the customer selects, appears alongside the building price and the manufacturer comparison.
How Concrete Slab Volume Is Calculated
The math behind every estimate. Concrete is sold by the cubic yard, and a cubic yard is 27 cubic feet.
Example: a 24 ft × 24 ft slab poured 4 inches thick is 24 × 24 × (4 ÷ 12) = 192 cubic feet, and 192 ÷ 27 = 7.1 cubic yards. Add a 10% waste factor for spillage, uneven grade, and forms, and the order becomes about 7.8 cubic yards. An 80 lb bag of pre-mix yields roughly 0.6 cubic feet, so bagged concrete only makes sense for very small pads.
Concrete for Common Metal Building Slabs
Cubic yards for the slab sizes dealers quote most often, at the thickness typically used for each building type. The last column adds a 10% waste factor.
| Building | Slab Size | Thickness | Cubic Yards | With 10% Waste |
|---|---|---|---|---|
| 12×21 Carport Pad | 12 ft × 21 ft | 4 in | 3.1 yd³ | 3.4 yd³ |
| 20×20 Two-Car Garage Slab | 20 ft × 20 ft | 4 in | 4.9 yd³ | 5.4 yd³ |
| 24×24 Two-Car Garage Slab | 24 ft × 24 ft | 4 in | 7.1 yd³ | 7.8 yd³ |
| 24×30 Garage & Workshop Slab | 24 ft × 30 ft | 4 in | 8.9 yd³ | 9.8 yd³ |
| 30×40 Workshop Slab | 30 ft × 40 ft | 5 in | 18.5 yd³ | 20.4 yd³ |
| 40×60 RV Garage & Shop Slab | 40 ft × 60 ft | 6 in | 44.4 yd³ | 48.9 yd³ |
Thicknesses shown are common starting points, not engineering specs. Local code, soil conditions, and anchor requirements decide the final slab design.
Slab Thickness and Add-Ons
What the calculator recommends, and what a customer can add with one tap.
4-Inch Slab
The standard for carports and residential garages holding cars, trucks, and SUVs. The calculator's default for most standard builds.
5-Inch Slab
Workshops and buildings that see heavier vehicles, lifts, or equipment. A common step up when the customer plans to work on trucks or store a tractor.
6-Inch Slab
RV garages, commercial buildings, and heavy equipment storage. Recommended when the load is a motorhome, a fifth wheel, or machinery.
Rebar or Wire Mesh
Reinforcement that controls cracking and carries the load. Added as a line item so the customer sees the cost next to the benefit.
Vapor Barrier
A sheet under the slab that keeps ground moisture out of an enclosed garage or shop. Priced in with one tap.
Thickened Edges
A turned-down perimeter that acts as a footing for the walls. Commonly required by code for enclosed buildings, and the permit tool flags it when it is.
Why Dealers Quote the Slab With the Building
The slab is the most common reason a metal building deal stalls after the deposit. Quoting it up front removes the surprise.
One Number, No Surprises
The customer sees steel, slab, and add-ons in one quote. Fewer cancellations when the concrete bid shows up, and fewer calls asking why it was not included.
Tied to Permits
The permit requirements tool pulls wind load, snow load, and setback rules for the customer's zip code, so the slab spec and the building spec come from the same source.
Free, Like Everything Else
The calculator is part of the SimpleLexi platform, which costs dealers nothing. No subscription, no setup fee, no per-user charge.
Concrete Slab Calculator FAQ
What is a concrete slab calculator?
A concrete slab calculator estimates how much concrete a slab needs from its length, width, and thickness, usually in cubic yards, and often adds an estimated cost. The SimpleLexi Concrete Slab Calculator is built into the free SimpleLexi 3D configurator, so it reads the building footprint automatically and adds the slab to the quote.
How do you calculate concrete for a slab?
Multiply length in feet by width in feet by thickness in inches, divide by 12 to get cubic feet, then divide by 27 to get cubic yards. A 24 × 24 ft slab that is 4 inches thick works out to 7.1 cubic yards. Most contractors add a 5 to 10 percent waste factor, which brings that slab to about 7.8 cubic yards.
How thick should a concrete slab be for a metal building?
A 4-inch slab is standard for carports and residential garages. Workshops and buildings that hold heavier vehicles or equipment usually move to 5 or 6 inches, and RV garages and commercial buildings typically call for 6 inches. Local building codes, soil conditions, and anchor requirements govern the final spec, which is why the calculator pairs with the SimpleLexi permit requirements tool.
Does the calculator include rebar, vapor barrier, and thickened edges?
Yes. Rebar or wire mesh, a vapor barrier under the slab, and thickened (turned-down) edges at the perimeter can each be added to the estimate with one tap. Thickened edges are commonly required for enclosed buildings so the walls sit on a proper footing.
Does the SimpleLexi calculator estimate the cost of the slab?
Yes. The calculator adds an estimated concrete cost to the building quote based on slab size, thickness, and the selected add-ons. Concrete prices vary by region and by contractor, so the estimate is a planning number and the final price should be confirmed locally.
Is the concrete slab calculator free?
Yes. It is part of the SimpleLexi platform, which is 100% free for metal building dealers. There is no setup fee, no subscription, and no per-user charge.
Can customers use the calculator inside the widget on my website?
Yes. Everything in the full configurator, including the concrete slab calculator, permit lookup, and financing toggle, is available in the embeddable micro version that runs on your dealer site.
Who pours the slab?
A local concrete contractor pours the slab before the building is installed. SimpleLexi's parent company, Metal America, also operates Metal America Concrete, a free concrete calculator and quote service that dealers and customers can use to price the pour.
Quote the Slab With Every Building
SimpleLexi is free for dealers. Schedule a demo and see the concrete slab calculator inside a live quote.