Crossover at 2-3 cubic yards. Below: bagged is cheaper and avoids minimum-delivery fees. Above: bulk dramatically wins on cost ($130-200/cu yd bulk vs $225/cu yd bagged equivalent). For 1 cubic yard, bagged = 45 80-lb bags = $225 + your labor. Bulk minimum delivery = $130-200 + delivery fee $80-120 = $210-320 — similar but you skip 8+ hours of bag-mixing labor. For 3+ cubic yards, bulk is unambiguously better.

How many bags per cubic yard?

45 80-lb bags = 1 cubic yard. 60 60-lb bags = 1 cubic yard. 90 40-lb bags = 1 cubic yard. Each 80-lb bag yields ~0.6 cubic feet when properly mixed with water. The math: 27 cubic feet per cubic yard / 0.6 cubic feet per bag = 45 bags. Hardware stores sometimes have promotional pricing on 80-lb (most efficient size for bulk DIY); 60-lb is easier to lift but uses more bags.

What's the buffer for?

Add 5-10% above calculated volume. Reasons: spillage during pour, over-pour to ensure level finish, density variation in mix, slight forms shifting during pour, depth variation in subgrade. For tight jobs, 5%; for over-pour-acceptable jobs (slab on grade), 10%. Running short mid-pour is far more costly than slight over-buy: cold joints from delayed second pour weaken structural integrity.

What about delivery access?

Concrete trucks need: 12+ ft horizontal clearance, ground firm enough to support 35,000+ lb trucks, within 10-15 ft of pour site (truck's chute reach). Soft / muddy ground requires gravel or steel plate. Steep driveways may not be possible. If access is bad, pump truck rental ($200-500) extends reach 50-100+ ft via concrete pumping. Schedule access assessment with concrete supplier before delivery day.

How long does concrete take to cure?

Walk-on: 24-48 hours. Drive on: 7 days. Full strength: 28 days. Concrete continues gaining strength for years but reaches 90% of design strength at 28 days. Wet curing (covering with plastic / wet burlap for 7 days minimum) yields stronger concrete than letting it dry quickly. Cold weather slows curing; hot weather accelerates (and risks cracking from rapid water loss). Plan project around curing time.

What if I run out mid-pour?

Order more from supplier IMMEDIATELY (most concrete trucks have buffer or can shuttle). Cold joints (where pour stops and restarts after partial set) weaken structure. Don't wait — even 15-30 min delay creates cold joint risk. For critical structural pours (footings, foundations), some suppliers offer “just in time” second truck dispatch. Plan and order more than you need; suppliers credit unused returned concrete (“short load” fee may apply).

Home & Life · Free tool

Concrete Cubic Yards Calculator

Calculate cubic yards of concrete for slabs, footings, columns, or stairs — plus bag vs bulk cost. Free tool, instant results, no sign-up, browser-only.

Updated June 2026

Shape

Length (ft)Width (ft)Thickness (in)

Waste (%)Ready-mix $/cu ydBag price ($/80 lb)

Cubic feet

88.0

Cubic yards

3.26

80 lb bags

147

Cheaper

Bulk

Ready-mix delivery

$489

Bag method (147 bags)

$735

Includes 10% waste. Bulk ready-mix typically beats bags above ~1 cu yd — at smaller volumes, the delivery minimum makes bags cheaper.

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What it does

Concrete is sold in two formats: bulk ready-mix from a concrete truck (sold by cubic yards, $130-200/cu yd in 2024-2025 plus delivery fees) and bagged dry mix (sold at hardware stores, ~$5-7 per 80-lb bag, requires you to add water and mix). The math: volume = length × width × depth. Convert cubic feet to cubic yards by dividing by 27 (1 cu yd = 27 cu ft). Each 80-lb bag of concrete mix produces about 0.6 cu ft when mixed (so 45 bags per cubic yard). Crossover between bulk and bagged pricing is around 2-3 cubic yards: below that, bagged is cheaper and easier; above, bulk delivery dramatically beats bag count and labor. Always add 5-10% for spillage, over-pour, and density variation.

The calculator takes shape (slab / footing / column / stair / circular pad) and dimensions, then outputs: cubic feet, cubic yards, 80-lb bag count, 60-lb bag count, and cost comparison between bulk delivery and bagged. For a typical 12×20 ft × 4-inch slab: 80 cu ft = 3 cu yd = 135 80-lb bags. Bulk: ~$540-700 delivered. Bagged: ~$675-945. Bulk wins for this size. For a 4×8 ft sidewalk × 4-inch deep: ~10.7 cu ft = 0.4 cu yd = 18 bags. Bulk minimum delivery (typically 1 cu yd) makes bulk pricing $130-200 + delivery $80-120 = $210-320 total just for material; bagged 18 bags × $6 = $108. Bagged wins for small jobs.

Practical execution considerations: (1) Truck delivery requires accessibility — truck must reach within 10-15 ft of pour location, OR you need pump truck (additional $200-500 cost). Soft ground / steep driveways block trucks. (2) Pour timing critical — concrete starts setting in 30-90 minutes; need adequate labor + tools ready before truck arrives. (3) Weather — pour when temperature is 50-90°F. Below 40°F requires cold-weather mix or curing blankets (premium). Above 95°F mix sets too fast; pour early morning. (4) Bagged mixing — wheelbarrow + hoe works for under 10 bags; mortar mixer rental ($35-60/day) for more. Mixing is hard physical labor; plan for 2 hours per cubic yard with basic tools. (5) Reinforcement — most slabs need rebar or wire mesh (see rebar-spacing-calculator). (6) Curing — cover with plastic sheeting or wet burlap for 7 days minimum; concrete keeps gaining strength for 28 days. Don't walk on fresh concrete for 24 hours; don't drive on it for 7 days.

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How to use it

Pick shape: slab / footing / column / stair / circular pad.
Enter dimensions in feet and inches.
Read cubic feet, cubic yards, and bag count (80-lb and 60-lb).
Compare bulk delivery cost vs bagged cost.
Add 5-10% buffer for spillage and over-pour.

When to use this tool

Planning a concrete project — confirming volume needed.
Comparing bulk truck vs bagged DIY for cost.
Pre-purchase calculation for hardware store bag count.
Sanity-checking a concrete contractor's estimate.
Multi-pour project planning (e.g., 4 footings, 1 slab — sum totals).

When not to use it

Specialty concrete (high-strength, polished, decorative) — different mix designs and pricing.
Structural concrete (load-bearing walls, foundations) — needs licensed engineer specs.
Pumpable / self-leveling concrete — different volumes and tools.
Specific contractor billing — calculator estimates material; labor / overhead is separate.

Common use cases

Pre-decision sanity-check on inputs and outputs
Educational use — demonstrating the underlying concept
Onboarding a colleague who needs the same calculation/conversion
Verifying a number or output before passing it on

Frequently asked questions

Bulk or bagged?: Crossover at 2-3 cubic yards. Below: bagged is cheaper and avoids minimum-delivery fees. Above: bulk dramatically wins on cost ($130-200/cu yd bulk vs $225/cu yd bagged equivalent). For 1 cubic yard, bagged = 45 80-lb bags = $225 + your labor. Bulk minimum delivery = $130-200 + delivery fee $80-120 = $210-320 — similar but you skip 8+ hours of bag-mixing labor. For 3+ cubic yards, bulk is unambiguously better.
How many bags per cubic yard?: 45 80-lb bags = 1 cubic yard. 60 60-lb bags = 1 cubic yard. 90 40-lb bags = 1 cubic yard. Each 80-lb bag yields ~0.6 cubic feet when properly mixed with water. The math: 27 cubic feet per cubic yard / 0.6 cubic feet per bag = 45 bags. Hardware stores sometimes have promotional pricing on 80-lb (most efficient size for bulk DIY); 60-lb is easier to lift but uses more bags.
What's the buffer for?: Add 5-10% above calculated volume. Reasons: spillage during pour, over-pour to ensure level finish, density variation in mix, slight forms shifting during pour, depth variation in subgrade. For tight jobs, 5%; for over-pour-acceptable jobs (slab on grade), 10%. Running short mid-pour is far more costly than slight over-buy: cold joints from delayed second pour weaken structural integrity.
What about delivery access?: Concrete trucks need: 12+ ft horizontal clearance, ground firm enough to support 35,000+ lb trucks, within 10-15 ft of pour site (truck's chute reach). Soft / muddy ground requires gravel or steel plate. Steep driveways may not be possible. If access is bad, pump truck rental ($200-500) extends reach 50-100+ ft via concrete pumping. Schedule access assessment with concrete supplier before delivery day.
How long does concrete take to cure?: Walk-on: 24-48 hours. Drive on: 7 days. Full strength: 28 days. Concrete continues gaining strength for years but reaches 90% of design strength at 28 days. Wet curing (covering with plastic / wet burlap for 7 days minimum) yields stronger concrete than letting it dry quickly. Cold weather slows curing; hot weather accelerates (and risks cracking from rapid water loss). Plan project around curing time.
What if I run out mid-pour?: Order more from supplier IMMEDIATELY (most concrete trucks have buffer or can shuttle). Cold joints (where pour stops and restarts after partial set) weaken structure. Don't wait — even 15-30 min delay creates cold joint risk. For critical structural pours (footings, foundations), some suppliers offer “just in time” second truck dispatch. Plan and order more than you need; suppliers credit unused returned concrete (“short load” fee may apply).

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