Ordering too little concrete means an expensive second delivery and a cold joint in your slab. Ordering too much means paying for waste. This calculator takes the guesswork out by converting your project dimensions to exact cubic yards needed, then adds the industry-standard 10% overage for waste and spillage. A typical 10x10 foot patio at 4 inches thick requires about 1.23 cubic yards — roughly 50 bags of 80-pound premix or one small ready-mix delivery. For anything over 1 cubic yard, ready-mix delivery is almost always more cost-effective and produces better results than mixing bags by hand.
Concrete Calculator
How to Use This Calculator
- Enter the length and width of your pour area in feet
- Set the thickness — 4 inches is standard for patios and walkways, 6 inches for driveways and garage floors
- View the cubic yards needed with built-in waste factor
- Check the bag count if mixing by hand — an 80-pound bag makes 0.6 cubic feet
- Compare estimated cost for bagged vs ready-mix delivery for your volume
How It Works
This concrete calculator uses established formulas to provide accurate results.
The basic rule:
- Volume (slab) = Length × Width × Depth
- 1 cubic yard = 27 cubic feet
- Add 10% extra for waste, spillage, and uneven sub-grade
Material prices and building codes vary by region. Get local quotes before purchasing.
Tips & Considerations
- Always order 10% more than calculated. Running short mid-pour creates a cold joint that weakens the slab and looks terrible.
- Ready-mix concrete typically costs $120-$160 per cubic yard delivered. Bags cost $5-7 each and make 0.6 cubic feet — above 1 cubic yard, ready-mix is cheaper and better.
- Temperature matters enormously. Do not pour when overnight temperatures will drop below 40°F, and avoid pouring when it is above 90°F unless you have experience with hot weather techniques.
- A standard mixer truck holds 8-10 cubic yards. Most companies charge a short load fee for orders under 3-4 yards.
Frequently Asked Questions
How many bags of concrete do I need for a 10x10 slab?
A 10x10 foot slab at 4 inches deep requires approximately 1.23 cubic yards of concrete. That is about 56 bags of 80-lb concrete mix, 72 bags of 60-lb mix, or 112 bags of 40-lb mix (including 10% for waste). For slabs larger than 2 cubic yards, consider ordering ready-mix delivery as it is more cost-effective and provides a better pour.
How thick should a concrete slab be?
Standard sidewalks and patios use 4-inch slabs. Driveways should be at least 4 inches thick, with 5-6 inches recommended for heavy vehicles. Garage floors are typically 4-6 inches. Footings for structures usually require 8-12 inches minimum. Always check local building codes, as requirements vary by location and intended use.
Is it cheaper to mix your own concrete or order ready-mix?
For small projects under 1 cubic yard (about 45 bags), mixing your own is usually cheaper at $250-$350 per yard. Ready-mix delivery costs $125-$200 per cubic yard but has minimum order requirements (usually 1-3 yards) and may charge short-load fees. For projects over 2 cubic yards, ready-mix is almost always more cost-effective and produces a more consistent, workable mix.
How long does concrete take to cure?
Concrete reaches initial set in 24-48 hours and can bear foot traffic after about 24 hours. It reaches approximately 70% of its full strength at 7 days and is considered fully cured at 28 days. During the first 7 days, keep the surface moist (curing compound or wet burlap) and protect from freezing temperatures. Avoid placing heavy loads for at least 7 days.
What is the difference between concrete and cement?
Cement is just one ingredient in concrete — it is the powder (Portland cement) that acts as the binder. Concrete is the finished product made by mixing cement with sand, gravel (aggregate), and water. Concrete mix bags from the hardware store contain all these ingredients pre-mixed. You can also buy pure cement to mix your own ratios, but pre-mixed bags are much more convenient for DIY projects.