Concrete Slab Calculator
Designed for flat rectangular slabs. Enter length, width, and slab thickness to estimate ready-mix volume or bagged concrete for smaller pours.
Step 2
Enter project measurements
Use decimals if needed (e.g. 3.5).
Step 3
How to use this calculator
Use inside form dimensions. Thickness is usually 4 in for patios and 4–6 in for driveways depending on loads and local code.
What the math is doing
Slab volume is length × width × thickness, identical to the general concrete calculator but framed for flatwork.
How to measure
Snap chalk lines and measure between forms. If the slab tapers, split it into rectangles and sum volumes.
Frequently asked questions
What thickness should I use?
Many residential patios use 4 in. Driveways and garage slabs often use 4–6 in with reinforcement.
Do I need a vapor barrier?
Under interior slabs on grade, yes. Patios vary by climate and local practice.
How do I account for footers?
Calculate footers separately as prisms and add volumes.
Is fiber mesh a substitute for rebar?
They solve different problems; follow engineer or code guidance for structural slabs.