Concrete Depot
Concrete Calculators & Tools
Concrete Floor Thickness Calculator
Estimate a practical floor thickness, concrete volume, bags, and cost based on floor type, load use, and subbase condition.
Thickness inputs
Choose floor use and dimensions. Results update live.
Used in the PDF report and saved report.
Switches starter units only.
◆ Recommended: 4 in thick · 3,000–4,000 PSI mix
Higher load can need more thickness.
Weak base can increase thickness.
Does not reduce thickness in this estimate.
10% is common for normal jobs.
Waste cannot be negative.
Optional cost per cubic yard.
Price cannot be negative.
Use waste volume for safer ordering.
Live 3D floor preview
The same SVG is used in the report.
Length
20 ft
Width
12 ft
Thickness
4 in
Result dashboard
Recommended thickness and material estimate.
Recommended floor thickness
Based on selected floor type and site conditions.
4 in
Typical range
4 in
Floor area
240 sq ft
Order volume
3.26 cu yd
Concrete needed
2.96 cu yd
40 lb bags
294 bags
60 lb bags
196 bags
80 lb bags
147 bags
Estimated cost
$456.30
Residential slab recommendation: 4 in thick · 3,000–4,000 PSI mix. This is a planning estimate. Ask an engineer for heavy loads, weak soil, or code-controlled work.
Formula used
The report includes these same steps.
Thickness rule: Base floor thickness + load adjustment + subbase adjustment
Volume formula: Volume = Length × Width × Recommended Thickness
Unit note: All measurements are converted to feet before volume is calculated.