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ACI-318 Compliant • Engineering Logic

Free Concrete Calculator for Construction Projects

This free concrete calculator estimates volume, weight, and bag counts for slabs, footings, and columns using industry-standard formulas.

CALCULATE CONCRETE No Sign-up Required • Works Offline

Target Audience

Designed for contractors, estimators, and DIY builders who need fast, accurate material quantities before ordering.

ID: USER_PRO

System Outputs

Outputs include total concrete volume (cubic yards), bag counts, material weight, and recommended waste allowances.

ID: DATA_OUT

Engineering Logic

A free construction calculator platform that helps estimate materials using engineering-grade formulas and industry standards.

ID: STD_ACI
Professional Tools

Calculators by Trade

Each calculator is designed to answer common construction questions like how much concrete you need, how many bags to buy, and how to estimate materials accurately before ordering.

REF: SPEC-2025-V2
03

Div 03 Concrete

Calculate cubic yards for slabs, footings, and columns. Includes ACI-318 compliant rebar logic and automated waste factors.

  • Cubic Yard Calculator
  • Bag Estimator (80lb/60lb)
  • Footing Logic
  • Sonotube Columns
06

Div 06 Carpentry

Estimate framing lumber for walls and floors. Supports 16" OC and 24" OC spacing logic.

  • Wall Studs
  • Floor Joists
31

Div 31 Earthwork

Determine material tonnage for driveways. Convert volume to weight for gravel & sand.

  • Gravel Tonnage
  • Compaction

Calculation Methodologies

How we calculate your materials.

Last Updated: December 2025 • Reviewed against ACI-318

Concrete Formulas

We use the standard formula: L × W × D / 27. This converts cubic feet into Cubic Yards. Bag counts are derived from standard yields (0.60 cu ft for 80lb bags).

Includes 5% Spillage Safety

Framing & Other Trades

Stud counts are calculated based on On-Center (OC) spacing plus corners/openings. Roofing squares are calculated at 100 sq ft per square with bundle waste factors included.

Supports 16" & 24" OC

Frequently Asked Questions

How much concrete do I need for a driveway?
To calculate driveway concrete, multiply Width x Length x Thickness (in feet). For a standard 20'x40' driveway at 4 inches thick, you need approximately 10 cubic yards. Always add 5-10% for spillage and waste.
How many cubic yards are in a concrete truck?
A standard ready-mix truck holds between 8 and 10 cubic yards of concrete. If your project requires 12 yards, you will need to schedule two trucks or pay a "short load" fee for small deliveries.
What is the formula for calculating concrete cubic yards?
To calculate cubic yards, multiply Length (ft) × Width (ft) × Depth (ft) to get cubic feet. Then, divide the total by 27.

Example: A 10'x10' slab at 4 inches deep (0.33 ft) is 33 cubic feet. Divided by 27, that is 1.22 cubic yards.
How many 80lb bags of concrete are in a yard?
It takes 45 bags (80lb) to equal one cubic yard of concrete. If you are using smaller 60lb bags, you will need 60 bags per yard.
How do you calculate studs for a wall (Framing Estimate)?
For 16-inch on-center spacing, convert your wall length to inches and divide by 16. Always add: +1 end stud, +2 studs per corner, +2 studs per opening.
Pro Tips

Recommended Waste Factors

The #1 cost overrun is estimating errors. Add these safety margins to your Net Volume:

  • Concrete Slabs 5-10%
  • Framing Lumber 15%
  • Drywall 10%
  • Roofing 10-15%

Field Reference & Constants

REF_DB_2025

Concrete (3000 PSI)

Wet Density 4,050 lbs/yd³
80lb Bags / Yd³ 45 Bags
60lb Bags / Yd³ 60 Bags
Slab Weight (4") ~50 lbs/sq ft

Lumber & Waste

16" OC Logic 1 stud / 12"
Standard Waste 10% - 15%
Drywall Weight 50 lbs / sheet
Stud Trim Height 92 5/8"

Roofing Systems

Bundles / Sq 3 Bundles
Nails / Sq ~320 Nails
Underlayment 2 Rolls / 10 sq
Weight / Sq 240 lbs

Soil & Aggregate

Gravel (Loose) 2,500 lbs/yd³
Topsoil (Loose) 2,100 lbs/yd³
Swell Factor +20%
Compaction -15%