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Concrete Calculator — Cubic Yards, Bags & Cost

Calculate exactly how much concrete you need for slabs, footings, sidewalks, or driveways. Results in cubic yards, 80lb bags, 60lb bags, and total cost.

Enter your dimensions

Your result

Cubic Yards (with waste)
1.36yd³
What to order
Cubic Yards (exact)
1.23yd³
Bags (80 lb pre-mix)
56bags
Bags (60 lb pre-mix)
75bags

How to use this concrete calculator

Enter the length, width, and thickness of your concrete project in feet and inches. The calculator returns four numbers: cubic yards with waste included (what you actually order), cubic yards exact, 80lb pre-mix bag count, and 60lb pre-mix bag count.

For L-shaped or irregular pours, break the area into rectangles and add the results. For circular piers or footings, calculate π × radius² × depth separately and sum. Always add 10% waste minimum — concrete trucks won't come back for an extra half-yard without charging a short-load fee.

Concrete thickness guidelines

Getting thickness right matters more than most DIYers realize. Too thin and it cracks; too thick is just wasted money. Standard recommendations:

  • Sidewalks / walking paths: 4 inches
  • Patios (foot traffic only): 4 inches
  • Residential driveways: 4–6 inches (6" for heavy vehicles, RVs, or clay soils)
  • Garage slabs: 4 inches with fiber mesh or wire, 6" if heavy loads
  • Shed / outbuilding foundations: 4 inches over 4" compacted gravel base
  • Heavy equipment pads: 6–8 inches reinforced
  • Standard footings (residential): 8–12 inches wide by 12–24 inches deep (varies by frost line and local code)

Anything over 4 inches should have rebar or wire mesh reinforcement. For driveways, two layers of #4 rebar on 16-inch centers is typical residential spec.

Bags vs. ready-mix: when each makes sense

Under 1 cubic yard: bags are faster, cheaper, and don't require coordinating a truck.

  • A cubic yard of concrete = 60 bags of 60lb pre-mix OR 45 bags of 80lb pre-mix
  • Cost: ~$250–$400 in bags vs. ~$180–$220 for a short-load truck with delivery

1–2 cubic yards: gray area. Bags get expensive and labor-intensive (you'll be mixing 45+ bags). Consider a mobile mixer rental ($100/day) or a short-load truck if one's available in your area.

3+ cubic yards: ready-mix truck every time. Trucks hold 8–10 yards typically, and delivery is cheaper per-yard at volume. Minimum delivery is usually 3 yards in most markets.

Ready-mix concrete averages $140–$180 per cubic yard in the US, plus delivery fees ($50–$150) and short-load fees if under the minimum ($50–$75 per yard short).

How long you have to work with concrete

This is where most DIY pours go wrong. Once concrete is mixed and poured:

  • Initial setting: 30–60 minutes — must be in final position
  • Working time: 60–90 minutes from truck arrival — finishing and edging complete
  • Walking on it: 24 hours minimum
  • Light vehicle traffic: 7 days
  • Full cure strength: 28 days (though usable at 7)

Temperature matters. Above 90°F, working time drops to 45 minutes. Below 50°F, concrete cures slowly and needs blankets. Ideal pour temperature is 50–80°F.

For DIY pours over 1 cubic yard, line up 2–3 helpers before the truck arrives. Have your forms set, rebar placed, subgrade wet down, and tools ready. Amateur hour starts when the chute opens.

What's in the mix: PSI ratings explained

Concrete is rated by compressive strength (PSI at 28 days). Standard options:

  • 2,500 PSI: minimum residential code in most US markets. Fine for sidewalks.
  • 3,000 PSI: driveways, standard slabs, most residential work.
  • 4,000 PSI: heavy-duty driveways, garage slabs, high-traffic commercial.
  • 5,000+ PSI: structural, engineered applications only.

When you order ready-mix, you specify PSI. "3,000 pound mix" is the standard ask. Higher PSI costs more but is more crack-resistant and lasts longer. For driveways in freeze-thaw climates, pay the extra $10–$15/yard for 4,000 PSI — it's worth it.

Common mistakes to avoid

  • Under-ordering. Always add 10% waste minimum. Running short mid-pour is a nightmare — you can't pause concrete.
  • Skipping the gravel base. 4 inches of compacted crushed stone under any slab dramatically improves lifespan and drainage.
  • Forgetting control joints. Score or saw-cut joints every 8–12 feet to control where cracks form. Concrete will crack; joints just make the cracks happen where you want.
  • Pouring in bad weather. Rain before it sets = ruined surface. Frost = structural damage. Hot sun = rapid cure before finishing.
  • Walking on it too early. Footprints at 12 hours are permanent.

Frequently Asked Questions

How much concrete do I need for a 10x10 slab?+
A 10 × 10 foot slab at 4 inches thick needs 1.23 cubic yards of concrete (1.35 with 10% waste). That's 56 80lb bags or 74 60lb bags. At 6 inches thick, you need 1.85 cubic yards.
How many bags of concrete in a cubic yard?+
A cubic yard of concrete = 45 bags of 80lb pre-mix OR 60 bags of 60lb pre-mix OR 90 bags of 40lb pre-mix. This assumes standard dry pre-mix like Quikrete or Sakrete. The ratio stays constant regardless of brand.
How thick should a concrete driveway be?+
4 inches minimum for standard residential driveways. 6 inches for heavy vehicles (trucks, RVs) or clay soils with poor drainage. Anything over 4 inches should have rebar or wire mesh reinforcement. Commercial driveways are typically 6–8 inches.
How much does a yard of concrete cost?+
Ready-mix concrete costs $140–$180 per cubic yard in most US markets as of 2026. Add $50–$150 for delivery. Short-load fees apply under 3 yards (typically $50–$75 per yard short). Higher PSI mixes (4,000+) cost $10–$20 more per yard.
Can I pour concrete myself?+
Yes, for slabs up to about 1 cubic yard — that's roughly 45 bags of 80lb pre-mix. Beyond that, the logistics of mixing fast enough before initial set become impossible without a mobile mixer. For pours over 1 yard, order ready-mix and have helpers ready.
How long does concrete take to dry?+
Concrete sets within 30–60 minutes, is walkable in 24 hours, holds light vehicles after 7 days, and reaches full strength in 28 days. Don't drive on it before 7 days and don't park heavy vehicles before 28. Wet curing (keeping the surface damp for 3–7 days) improves final strength.
Do I need rebar in my concrete slab?+
For slabs thicker than 4 inches, driveways, garage floors, or any structural application, yes — rebar or welded wire mesh. For 4-inch sidewalks and patios with good base prep, fiber mesh mixed into the concrete is often sufficient and cheaper. Local code may require rebar regardless.
How much waste should I add to my concrete order?+
Add at least 10% waste to any concrete order. For complex shapes, slopes, or first-time DIY pours, 15%. Running short on delivery day means paying another full delivery fee plus short-load charges for a tiny top-up — often $300+ for missing half a yard.

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Written by TidyCalculator Team · Content team