Reinforced Concrete Slab Calculator
Calculate concrete volume, rebar mesh weight, and estimated material costs for solid slabs. Includes pre-mixed bag estimation and shrinkage waste factors.
1. Slab Dimensions
2. Reinforcement
3. Cost Estimation (Optional)
About
Casting a reinforced concrete slab requires accurate volumetric calculation to avoid cold joints caused by running out of material mid-pour. This tool computes the total volume of concrete required for floors, driveways, or pads, including a configurable safety margin (typically 5-10%) for subgrade unevenness and shrinkage.
Structural integrity depends on reinforcement. The calculator estimates the required Steel Rebar or Wire Mesh based on standard grid spacing (e.g., 12″ or 300mm OC). It integrates specific density constants for normal-weight concrete (2400 kg/m3 or 150 lb/ft3) and allows users to input local unit prices to generate a preliminary budget for the project.
Formulas
The core volume (V) is the product of Length (L), Width (W), and Thickness (T), adjusted by a waste factor (w):
Rebar length (Lsteel) is calculated by determining the number of bars in the X and Y directions based on spacing (s):
Bags of pre-mix concrete (Nbags) are derived from the total volume and the yield per bag (Ybag):
Reference Data
| Rebar Size (US) | Metric Equivalent | Weight (lb/ft) | Mass (kg/m) | Common Use |
|---|---|---|---|---|
| #3 | 10 mm | 0.376 | 0.560 | Patios, Driveways |
| #4 | 12-13 mm | 0.668 | 0.994 | Structural Slabs, Walls |
| #5 | 16 mm | 1.043 | 1.552 | Heavy Load Footings |
| #6 | 19-20 mm | 1.502 | 2.235 | Beams, Columns |
| #7 | 22 mm | 2.044 | 3.042 | Retaining Walls |
| #8 | 25 mm | 2.670 | 3.973 | Commercial Foundations |