CALC-001 · DRAWING NO. C-001 · REV A
Concrete slab calculator.
Drafted to scale · cited sources · honest numbers
Enter the slab dimensions. The calculator works out cubic yards, 80 lb bag equivalents, and a delivered-cost range from national-baseline ready-mix and bagged concrete pricing.
◈ DRAFTING PANEL · CONCRETE TAKEOFF · N.T.S.
SHEET C-001 · REV A
Redline · scope notice Materials takeoff only. Does not evaluate subgrade, reinforcement, frost depth, or structural loading. Consult ACI 332 or a licensed engineer for any structural pour.
Note 01 · Field Procedure
How to measure the pour
- Square the forms. Lay out the form boards and measure the inside dimension on the long side. Check that the diagonals are equal before recording anything.
- Record length and width in feet, inside the forms. Round up to the nearest half foot for irregular edges.
- Measure thickness from the top of the compacted gravel base to the top of the form board, not to ground level.
- Check for a crown in the subgrade. If it dips in the middle, add 0.5 inch to thickness. The crown is the #1 reason DIY pours run short.
- Rectangles only. L-shaped patios, curved pads, and dog-ears: break into rectangles, run the calc once per rectangle, and sum the cubic yards at the end.
Note 02 · Equation
The formula
yd³ = ( L × W × T ) ÷ 324 × ( 1 + waste ÷ 100 )
Llength in feet
Wwidth in feet
Tthickness in inches
324ft³→yd³ factor for T in inches (12 × 27)
Note 03 · Sanity Ranges
Typical slab thicknesses
| T | Use case | Notes |
|---|---|---|
| 4" | Patio / shed floor / walkway | Non-structural, light foot traffic. |
| 5" | Heavy walkway | #3 rebar at 18" o.c. in freeze-thaw zones. |
| 6" | Residential driveway | Passenger cars; rebar or WWM required. |
| 8"+ | RV pad / workshop / garage | Engineer-designed; stamped drawing. |
Note 04 · References
Sources
Authorities cited on this sheet
- ACI 332-20: Residential Code Requirements for Structural Concrete · American Concrete Institute. Defines minimum thicknesses, reinforcement schedules, and aspect-ratio limits for residential concrete slabs. Paid standard; the ACI store page is the canonical link. For free residential slab guidance, see the NRMCA CIP series below.
- Quikrete 80 lb Concrete Mix Technical Data Sheet · Yield 0.6 ft³/bag, the basis for the 80 lb bag count line on the spec slip.
- NRMCA Concrete in Practice information series · National Ready Mixed Concrete Association reference library on ready-mix delivery, short-load fees, and pour preparation.
PROJ MATERIALFOREMAN
SHT C-001 / 014
REV A · 2026-04-19
DRAWN MF