Concrete Calculator & Concrete Resource Center
Calculate concrete yards, bags, cost, and waste for slabs, driveways, patios, footings, post holes, walls, and columns. Then use the guides below to plan your pour, compare bagged concrete and ready-mix, choose materials, repair concrete, and learn about concrete testing, careers, and certifications.
Concrete
Mix
3×3×3 ft
This concrete resource center helps homeowners, DIY builders, students, workers, and construction professionals estimate concrete quantities, plan pours, compare bagged concrete and ready-mix, choose tools and materials, repair existing concrete, and understand concrete careers, certifications, testing, and inspection.
Concrete Calculator
Estimate concrete yards, bags, waste, and cost
Use the calculator for slabs, driveways, footings, walls, columns, and post holes. The result separates bagged concrete from ready-mix so you can choose the right buying path.
Calculate Concrete Needed
Enter project dimensions to estimate raw volume, waste-adjusted volume, bag count, weight, and cost.
Concrete Results
Your estimate updates when you calculate.
| Bag Size | Approx. Yield | Bags Needed |
|---|---|---|
| 40 lb | 0.30 ft³ | 123 |
| 50 lb | 0.375 ft³ | 99 |
| 60 lb | 0.45 ft³ | 82 |
| 80 lb | 0.60 ft³ | 62 |
Formula: length × width × thickness ÷ 27 = cubic yards. Add waste factor after calculating raw volume.
Save or use this estimate
Print the estimate, copy it, or continue to related concrete resources below.
Quick Answer
How much concrete do I need?
The most common way to estimate concrete is to calculate the project volume, convert it to cubic yards, and add a waste factor before ordering.
Concrete volume formula
For a rectangular slab, patio, sidewalk, driveway, footing, or wall, multiply the length, width, and thickness. If your dimensions are in feet, divide cubic feet by 27 to get cubic yards.
Cubic yards = length ft × width ft × thickness ft ÷ 27 If thickness is inches: cubic yards = length ft × width ft × thickness in ÷ 324Add 5% to 15% extra for waste, uneven subgrade, form variation, spillage, or measurement uncertainty. A 10% waste factor is a practical default for many small concrete projects.
Example: 10 ft × 10 ft slab at 4 inches thick
Use the inch-thickness shortcut:
10 × 10 × 4 ÷ 324 = 1.23 yd³Then add 10% waste:
1.23 × 1.10 = 1.36 yd³ to orderUsing 80 lb bags at about 0.60 ft³ per bag, that is approximately 62 bags. For this size, compare bagged concrete, mixer rental, and ready-mix options before buying.
Concrete Calculators
Search concrete calculators, guides, and resources
Find a calculator or guide for slabs, bags, driveways, footings, fence posts, reinforcement, gravel base, repair, testing, and cost planning.
Concrete Calculator
Estimate cubic yards, bags, waste, cost, and ready-mix volume for general concrete projects.
Open calculator →Concrete Slab Calculator
Calculate concrete for patios, sidewalks, shed pads, garage slabs, and rectangular flatwork.
Open calculator →Concrete Bag Calculator
Estimate how many 40 lb, 50 lb, 60 lb, or 80 lb bags of concrete mix you need.
Open calculator →Concrete Cost Calculator
Estimate ready-mix, bagged concrete, delivery, forms, reinforcement, labor, and total cost.
Open calculator →Concrete Driveway Calculator
Estimate driveway concrete, base gravel, reinforcement, joints, cost, and ready-mix quantity.
Open calculator →Fence Post Concrete Calculator
Calculate bags for fence posts, mailbox posts, deck posts, gate posts, and round post holes.
Open calculator →Concrete Footing Calculator
Estimate concrete for continuous footings, square footings, foundation footings, and structural pours.
Open calculator →Rebar Calculator
Estimate rebar quantity, spacing, lap length, grid layout, and reinforcement needs.
Open calculator →Gravel Base Calculator
Estimate crushed stone or gravel base for slabs, driveways, patios, sidewalks, and flatwork prep.
Open calculator →Cost, Bags & Ready-Mix
Decide what to buy and how to order
Bag count, ready-mix ordering, cost per yard, delivery, and waste factor are some of the most useful concrete planning topics.
| Project Size | Likely Best Option | Why | Best Next Step |
|---|---|---|---|
| Under 0.25 yd³ | Bagged concrete | Small repairs, posts, and patches are practical to mix by hand. | Use the concrete bag calculator |
| 0.25–0.75 yd³ | Bags or mixer rental | Still possible as DIY, but the number of bags can become labor-heavy. | Compare bags and tools |
| 0.75–1.5 yd³ | Compare all options | Bag count becomes high. Short-load ready-mix or mixer rental may be better. | Compare bags vs ready-mix |
| 1.5–3 yd³ | Ready-mix likely better | Hand mixing can be difficult, slow, and inconsistent. | Plan ready-mix delivery |
| 3+ yd³ | Ready-mix strongly recommended | Larger pours need speed, consistency, crew planning, and finishing tools. | Prepare a full pour checklist |
| Slab Size | Thickness | Raw Cubic Yards | 80 lb Bags Approx. | With 10% Waste |
|---|---|---|---|---|
| 4 ft × 4 ft | 4 in | 0.20 yd³ | 9 bags | 10 bags |
| 6 ft × 6 ft | 4 in | 0.44 yd³ | 20 bags | 22 bags |
| 8 ft × 8 ft | 4 in | 0.79 yd³ | 36 bags | 40 bags |
| 10 ft × 10 ft | 4 in | 1.23 yd³ | 56 bags | 62 bags |
| 12 ft × 12 ft | 4 in | 1.78 yd³ | 80 bags | 89 bags |
| 20 ft × 20 ft | 4 in | 4.94 yd³ | 223 bags | 247 bags |
| Project | Common Planning Thickness | Notes | Best Calculator |
|---|---|---|---|
| Sidewalk | 4 in | Common for pedestrian use. Verify local requirements. | Concrete Slab Calculator |
| Patio | 4 in | Increase thickness or reinforcement for heavier loads or poor base conditions. | Concrete Patio Calculator |
| Shed slab | 4 in | Depends on shed weight, equipment, and subgrade support. | Concrete Slab Calculator |
| Driveway | 4–6 in | Vehicle loads, base prep, joints, and reinforcement matter. | Concrete Driveway Calculator |
| Garage slab | 4–6 in | Verify load requirements, reinforcement, vapor barrier, and local code. | Concrete Slab Calculator |
| Footing | Varies | Depends on loads, soil, frost depth, reinforcement, and local code. | Concrete Footing Calculator |
DIY Concrete Projects
Pour, mix, finish, and cure concrete correctly
DIY concrete projects require more than a volume estimate. Plan the base, forms, reinforcement, pour timing, finishing tools, joints, and curing.
A typical small concrete pour follows this sequence: measure the project, excavate to depth, compact the subgrade, place a gravel base if needed, build forms, add reinforcement when appropriate, pour the concrete, screed it level, float and edge the surface, add control joints, and cure the slab so it can gain strength properly.
Concrete Pouring & Project Guides
Use these guides to plan the job before buying materials or scheduling a pour.
| Common Mistake | Why It Matters | Best Supporting Page |
|---|---|---|
| Ordering too little concrete | Running short during a pour can create cold joints, delays, and poor finish quality. | Concrete Waste Factor Guide |
| Adding too much water | Extra water can weaken concrete and increase shrinkage and surface defects. | Concrete Mix Ratio Guide |
| Poor base preparation | A weak or uneven base can lead to cracking, settlement, and drainage problems. | Gravel Base Calculator |
| No control joints | Concrete cracks naturally; joints help control where cracks form. | Concrete Control Joints |
| Poor curing | Concrete needs proper curing conditions to develop strength and durability. | Concrete Curing Explained |
Materials & Buying Guides
Concrete products, tools, and supplies
Use these guides to choose concrete mix, reinforcement, forms, repair products, sealers, and tools for the job.
Concrete Repair & Maintenance
Fix cracks, spalling, settling, stains, and worn concrete
Repair content helps users decide whether the issue is cosmetic, structural, drainage-related, or a sign of settlement.
Hairline cracks may only need cleaning and sealant, while wider cracks, uneven slabs, spalling, or recurring movement can point to drainage, base, freeze-thaw, reinforcement, or settlement problems. If the slab is moving, sinking, or supporting structural loads, get professional guidance.
Learn Concrete Basics
Concrete fundamentals for beginners, students, and DIY users
These definitions help users understand the material before they choose a mix, pour a slab, repair a crack, or study concrete testing.
A mixture of cement, water, sand, aggregate, and sometimes admixtures that hardens into a stone-like material.
The binder ingredient in concrete. Cement is not the same thing as concrete.
A compressive strength rating that describes how much load hardened concrete can resist.
The process of maintaining moisture and temperature so concrete can gain strength properly.
A field test that indicates fresh concrete workability and consistency.
Steel rebar or wire mesh used to help concrete resist tension and control cracking.
Concrete Careers & Certifications
Work in concrete, get trained, and understand certification paths
Concrete work includes laborers, finishers, testing technicians, inspectors, estimators, suppliers, and contractors.
| Career Path | What They Do | Useful Content Path |
|---|---|---|
| Concrete laborer | Preps forms, moves material, helps place concrete, cleans tools, and supports the crew. | Entry-level concrete jobs guide |
| Concrete finisher | Screeds, floats, edges, joints, textures, and finishes slabs and flatwork. | Concrete finisher career guide |
| Concrete testing technician | Performs fresh concrete field tests such as slump, temperature, air, and cylinders. | ACI Field Testing Technician Grade I guide |
| Concrete inspector | Reviews placement, testing, specifications, reinforcement, and quality-control documentation. | Concrete inspector career guide |
| Concrete contractor | Estimates jobs, manages crews, schedules pours, coordinates suppliers, and oversees quality. | Concrete estimating and business guides |
Career & Certification Topics
Concrete Testing & Inspection
Professional concrete quality, testing, and inspection topics
Testing and inspection content gives the hub professional depth and supports certification, engineering, and quality-control search intent.
| Test or Topic | What It Checks | Who Uses It |
|---|---|---|
| Slump test | Fresh concrete workability and consistency. | Field testing technicians, inspectors, contractors. |
| Concrete cylinders | Compressive strength after curing and lab testing. | Testing labs, inspectors, engineers. |
| Air content | Entrained or entrapped air in fresh concrete. | DOT work, cold-weather concrete, QC teams. |
| Concrete temperature | Placement conditions that affect set time and performance. | Field crews, testing technicians, inspectors. |
| Mix design | Proportions and performance requirements for concrete mixtures. | Engineers, suppliers, QC teams. |
Project Checklist
Save your concrete planning checklist
Before you buy materials, confirm dimensions, waste factor, bag count or ready-mix volume, base prep, forms, reinforcement, tools, weather, crew, finishing, and curing.
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