Flatwork
& Slab
Calculators
Ten calculators covering every horizontal concrete surface — from a basic backyard slab to a stamped pool deck, a resurfaced garage floor, or a self-leveling overlay. Enter your dimensions, get your volume, bag count, and waste-adjusted order quantity in seconds.
Flatwork & Slab Calculators
Every horizontal concrete surface has its own geometry quirks and typical thickness requirements. Pick the right calculator for your project below.
The foundational tool for any flat pour. Enter length, width, and thickness — get cubic yards, cubic feet, bags (40/60/80 lb), and a waste-adjusted ready-mix order quantity. Supports rectangular, circular, and L-shaped slabs in imperial and metric.
Optimized for driveway geometry — single, double, and curved layouts. Includes recommended 4–6″ thickness guidance based on vehicle type (passenger cars vs. trucks and RVs).
Calculate concrete volume for rectangular, freeform, and multi-section patios. Includes optional coverage for stamped or colored finishes and typical 3.5–4″ residential thickness.
Long, narrow runs with consistent width — walkways, garden paths, and public sidewalks. Accounts for standard 4″ pedestrian thickness and ADA slope requirements where relevant.
Garage floors take a beating. This calculator targets 4–6″ thickness based on use (personal vehicle vs. workshop vs. heavy equipment) and includes apron transition area if needed.
Compact pads for sheds, AC units, generators, and heavy equipment. Handles non-standard dimensions and recommends minimum 4–6″ depth depending on point-load requirements.
Pool deck geometry is tricky — border strips, coping overhangs, and irregular shapes around the pool perimeter. Enter pool dimensions and deck width to get the net concrete area and volume.
Stamped pours need the same volume math as any slab, plus estimates for integral color pigment quantities, release agent coverage, and sealer square footage. All consolidated here.
Calculates the volume of concrete resurfacer or micro-overlay product needed based on surface area and application thickness — typically 1/8″ to 1/2″ for bonded overlays.
Self-leveling underlayment quantities depend on average pour depth over an uneven substrate. Enter room dimensions and average depth variation to get bags of SLU compound needed.
Flatwork Is Where Most Concrete Gets Poured — and Most Mistakes Get Made
Flatwork accounts for the majority of residential and light commercial concrete volume. It's also where ordering errors are most common — because the math looks simple until you account for thickness variations, irregular shapes, and the inevitable short pour if you underestimate by even half an inch of depth across a large area.
The most important variable in flatwork is thickness, and it's the one most often skimped on. ACI 302.1R recommends a minimum 4-inch slab thickness for pedestrian-only surfaces (patios, sidewalks) and 5–6 inches for vehicular traffic. Every half-inch of additional depth on a 20×20 slab adds roughly 0.6 cubic yards — that's a meaningful cost and structural difference, not a rounding error.
Sub-base preparation matters as much as the concrete itself. A properly compacted 4-inch gravel base reduces differential settlement, improves drainage, and dramatically extends slab life. Our calculators output the concrete volume for the finished slab — use the Gravel Calculator to size the sub-base separately.
For decorative applications like stamped concrete, the volume math is identical to a plain slab — the difference is in the pigment, release agent, and sealer quantities that need to be ordered alongside the concrete. The Stamped Concrete Calculator handles all of that in one place.
From Backyard DIY to Commercial Flatwork
These calculators are used at every project scale — the math is the same whether you're pouring a 10×10 patio or a 10,000 sq ft warehouse floor.
Homeowners & DIYers
Figuring out how many bags to buy for a patio or driveway before heading to the hardware store. The Slab Calculator and Driveway Calculator give you a bag count plus a ready-mix order quantity so you know whether to DIY or call a truck.
Concrete Contractors
Fast quantity checks before submitting bids. Use the multi-section slab and pool deck calculators for complex geometry, then feed the volume into the Cost Calculator for a complete material estimate.
Estimators & Project Managers
Verify subcontractor takeoffs on flatwork packages. The resurfacing and floor leveling calculators are particularly useful for renovation projects where overlay quantities are often estimated loosely and ordered short.
Flatwork & Slab Questions
The most common questions about concrete slabs, thickness requirements, and ordering.
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