ConstructionCalc
Field referenceUpdated Jun 2026Yields QuikreteDensity ACIPrice NRMCA 2024

Ready-mix concrete

Concrete Calculator: How Much Concrete You Need? + Cost

Tell us your shape and dimensions — we'll tell you exactly how much concrete to order in cubic yards, bags, weight and cost, for slabs, footings, columns, walls and stairs, in both imperial and metric.

Yards · Bags · Weight · Cost6 shapesImperial + MetricQuikrete yieldsNRMCA price

Here's the deal

Starting a pour and not sure how much to order? Pick your shape, punch in the dimensions, choose your bag size, and you'll walk away with cubic yards, a bag count, the weight, and a material cost — no guesswork, no second delivery. We've got this.

Figuring concrete for:

A patio slab?A footing or foundation?Sonotube columns?A garage or shed floor?Concrete steps?
A 10 × 10 ft slab at 4 inches needs about 1.36 cubic yards — 62 eighty-pound bags. Ready-mix runs roughly $160–195 per cubic yard; enter any shape and size below for your number.

Concrete is sold two ways, and the calculator handles both. Ready-mix is delivered by the truck and priced per cubic yard; bagged concrete is mixed on site and priced per bag. Knowing both numbers up front tells you which is cheaper for your job and stops you ordering short.

Every figure here is computed from the dimensions you enter and standard, sourced constants — bag yields from the manufacturer, density from ACI normal-weight values, and a ready-mix price range anchored to industry data. Nothing is guessed; the methodology page shows exactly where each number comes from.

yield 0.6 ft³/bag — Quikrete spec, research §3
LENGTHWIDTHTHICKNESSlength × width × thickness = concrete

Rectangular slab — length × width × thickness.

= 3.05 m
= 3.05 m
= 10.2 cm

Enter your measurements,
then hit Calculate

Your full breakdown — yards, tons, bags, loads and cost — appears here.

Step 1

How to measure each shape

Six shapes, six small diagrams. Pick the one that matches your project, take the dimensions called out in the diagram, and enter them above.

LENGTHWIDTHTHICKNESSlength × width × thickness = concrete
Slab
L × W × thickness

Measure length and width in feet, thickness in inches. A 6-inch slab uses 50% more concrete than a 4-inch slab over the same footprint.

DIAMETERTHICKNESSπ × (diameter ÷ 2)² × thickness = concrete
Round slab
π × (D ÷ 2)² × thickness

Measure the diameter across the widest point. A round pad uses about 21% less concrete than the square slab that would enclose it.

LENGTHWIDTHDEPTHlength × width × depth = concrete
Footing
L × W × depth

Measure the total run in feet, width and depth in inches. A continuous footing is a long rectangular prism.

DIAMETERHEIGHT× Nn × π × (diameter ÷ 2)² × height = concrete
Column / sonotube
n × π × (D ÷ 2)² × H

Measure tube diameter in inches and height in feet; enter the count. Four identical sonotubes are costed in one step.

LENGTHHEIGHTTHICKNESSlength × height × thickness = concrete
Wall
L × H × thickness

Measure length and height in feet, thickness in inches. A poured wall is a slab stood on its edge.

RISERUNWIDTH× n stepswidth × rise × run × n(n+1)/2 = concrete (solid pour)
Stairs (solid pour)
W × R × T × n(n+1)/2

Solid stair volume grows with the square of step count — doubling steps more than doubles the concrete.

Worked examples

Real projects, calculated step by step

Each example shows the geometric volume first, then the order volume (the calculator adds 10% — 15% for stairs — by default to cover spillage and uneven subgrade), and the 80-pound bag count at the order volume.

Slab12 × 12 ft patio at 4 inches

12 × 12 × (4 ÷ 12) = 48 ft³ = 1.78 yd³
+10% waste → order ≈ 1.96 yd³
88 × 80-lb bags · material ≈ $310–$380

The geometry is 12 × 12 × (4 ÷ 12) = 48 cubic feet, which is 1.78 cubic yards. Adding the default 10% for spillage and uneven subgrade, you would order about 1.96 cubic yards, or 88 eighty-pound bags. At the ready-mix range that material costs roughly $310–$380, though for under two yards bags are often the more practical buy.

Round slab10 ft diameter pad at 4 inches

π × 5² ≈ 78.5 ft² → × (4 ÷ 12) = 26.2 ft³ = 0.97 yd³
+10% waste → order ≈ 1.07 yd³
48 × 80-lb bags · material ≈ $170–$210

A 10-foot circle covers π × 5² ≈ 78.5 square feet, and at 4 inches that is 26.2 cubic feet, or 0.97 cubic yards. With waste you would order about 1.07 cubic yards — 48 eighty-pound bags — for an estimated $170–$210 in material. Note how the round pad uses about 25% less concrete than a 10 × 10 ft square slab at the same thickness.

Footing30 ft run, 16 inches wide, 8 inches deep

30 × (16 ÷ 12) × (8 ÷ 12) = 26.7 ft³ = 0.99 yd³
+10% waste → order ≈ 1.09 yd³
49 × 80-lb bags · material ≈ $170–$210

The volume is 30 × (16 ÷ 12) × (8 ÷ 12) = 26.7 cubic feet, or 0.99 cubic yards. Allowing 10% waste, order about 1.09 cubic yards, which is 49 eighty-pound bags or roughly $170–$210 of ready-mix. Footings are where coming up short is most costly, because a cold joint in a structural element is hard to fix.

Columnfour 12-inch sonotubes, 4 ft tall

π × 0.5² × 4 = 3.14 ft³ per tube · × 4 tubes = 12.6 ft³ = 0.47 yd³
+10% waste → order ≈ 0.51 yd³
24 × 80-lb bags · material ≈ $80–$100

One 12-inch tube holds π × 0.5² × 4 = 3.14 cubic feet, so four of them total 12.6 cubic feet, or 0.47 cubic yards. With waste that is about 0.51 cubic yards — 24 eighty-pound bags — for an estimated $80–$100. Setting all four in one batch keeps the mix consistent across the footings.

Wall24 ft long, 4 ft tall, 8 inches thick

24 × 4 × (8 ÷ 12) = 64 ft³ = 2.37 yd³
+10% waste → order ≈ 2.61 yd³
118 × 80-lb bags · material ≈ $420–$510

This wall contains 24 × 4 × (8 ÷ 12) = 64 cubic feet, or 2.37 cubic yards, rising to about 2.61 cubic yards with waste. That is 118 eighty-pound bags — well past the point where mixing by hand stops making sense, so ready-mix delivery (about $420–$510 in material) is the realistic choice here. See the interactive bag-versus-ready-mix breakeven in the concrete bag calculator.

Stairs4 steps, 4 ft wide, 7-inch rise, 11-inch run (solid pour)

4 × (7 ÷ 12) × (11 ÷ 12) × 10 = 21.4 ft³ = 0.79 yd³
+15% waste (stairs) → order ≈ 0.91 yd³
41 × 80-lb bags · material ≈ $150–$180

Using the solid-stair formula, the volume is 4 × (7 ÷ 12) × (11 ÷ 12) × 10 = 21.4 cubic feet, or 0.79 cubic yards. Stairs use a higher 15% waste allowance for complex forming, so you would order about 0.91 cubic yards, or 41 eighty-pound bags, for roughly $150–$180. An open-riser or formed stair over a sloped slab uses less than a solid pour.

Bagged concrete

Bag sizes compared

Bagged concrete is the same 4000 psi mix in different quantities. The bag size changes only how many you carry and mix.

BagYield per bagBags per cubic yardCoverage at 4″
40 lb0.30 ft³900.9 sq ft
50 lb0.375 ft³721.1 sq ft
60 lb0.45 ft³601.35 sq ft
80 lb0.60 ft³451.8 sq ft
Source: QUIKRETE Concrete Mix product spec (Model 110180), corroborated by Cemex.

Bags per cubic yard

9040 lb7250 lb6060 lb4580 lb
The 80-pound bag is the most economical per cubic foot — the default here, and the size most contractors reach for. Lighter bags cost more per cubic foot but are easier to handle solo. All four sizes use the same 4000 psi mix, so you can combine them in one pour as long as each batch keeps the same water ratio.

Decision

Bags or ready-mix?

The crossover is mostly about volume. Bags win on small jobs; ready-mix wins as soon as the truck is worth its trip.

011.523CUBIC YARDS~10 yd³ — full truckBags cheaperCROSSOVERReady-mix cheaper

Cubic yards · bagged vs delivered ready-mix

Choose bags when…

Your job is under about 1 cubic yard, you can mix at your own pace, and avoiding a short-load delivery fee tips the math toward bagged.

Choose ready-mix when…

You need more than ~1.5–2 cubic yards. Above that point, ready-mix delivery wins on both price and labor — and a full 10-yard truck has no short-load surcharge.

A full ready-mix truck carries about 10 cubic yards. Ordering less brings a short-load fee of roughly $50–80 per yard — that fee is what tips small jobs back toward bags. Try the concrete bag calculator for the interactive breakeven.

Cost

What a yard of concrete costs

$160–195
PER YD³ DELIVERED
2026 range, standard mix
$179.89
NRMCA 2024 ANCHOR
National average — frozen baseline
3–6%
RISE 2025–26
Material + labor + transport
The calculator's figure is material only. Labor, forms, finishing, and delivery surcharges are not included. Small orders under about 10 cubic yards carry a short-load fee, and sites more than 20 miles from the plant add a per-mile charge.

For a full installed estimate including labor, the concrete slab cost calculator escalates material live from the BLS ready-mix PPI and adds a typical labor range. The methodology page explains how we derive the material range without copying any single retailer's quote.

Weight

How much concrete weighs

150 lb/ft³
DENSITY
ACI normal-weight standard
~4,050 lb
PER CUBIC YARD
~2 US tons
PER CUBIC YARD
Subgrade + transport planning

Weight matters most on elevated pours and on weak or disturbed soil, where the slab's own mass is part of the design. For ground slabs on compacted subgrade it is usually informational, but it is there when you need it. For demolition weight, broken-rubble swell, dumpster sizing, and pallet/payload planning, see the concrete weight calculator.

Before you order

Tips for ordering

Order ~10% extra

Stairs use 15%. Coming up short mid-pour means a cold joint and a second trip — both cost more than the small overage.

Match thickness to load

Four inches for patios, walkways and shed pads; 5–6 inches for driveways and garage floors. Thickness is the biggest single cost driver.

Size the gravel base separately

Most slabs sit on compacted gravel. Use our gravel calculator to order the sub-base in the same planning session.

Questions

Concrete calculator FAQ

How much concrete do I need for a 10 × 10 slab?
A 10 × 10 ft slab at 4 inches needs about 1.36 cubic yards — 62 eighty-pound bags (the calculator above adds 10% for waste). A 6-inch slab uses 50% more concrete for the same footprint. Enter your exact dimensions above for the precise figure.
How many 80-pound bags make a cubic yard?
It takes about 45 eighty-pound bags to make one cubic yard, because each 80-pound bag yields roughly 0.60 cubic feet and a cubic yard is 27 cubic feet. A 60-pound bag yields 0.45 cubic feet, so it takes about 60 of them; a 40-pound bag yields 0.30 cubic feet, taking about 90.
When should I order ready-mix instead of bags?
Order ready-mix above about 1.5 to 2 cubic yards — roughly 68 to 90 eighty-pound bags. Below 1 cubic yard, bagged concrete is usually cheaper and more practical because you avoid the short-load fee. Between those points, the short-load surcharge is what tips the math.
How much does a yard of concrete cost?
Ready-mix runs about $160 to $195 per cubic yard delivered in 2026, against an NRMCA 2024 national average of $179.89. Small orders under about 10 cubic yards add a short-load fee of roughly $50 to $80 per yard, and long-distance delivery adds a per-mile charge.
How thick should a concrete slab be?
Four inches is standard for patios, walkways, and shed pads. Use five to six inches for driveways, garage floors, and any slab that carries vehicle loads.
How much does concrete weigh?
Normal-weight concrete is about 150 pounds per cubic foot, or roughly 4,050 pounds — about 2 US tons — per cubic yard. The exact figure varies a little with mix and moisture.
How much extra should I order for waste?
A 5 to 10% allowance is typical for slabs and footings to cover spillage and uneven subgrade. Stairs and complex forming warrant 15 to 20%, which is why the calculator raises the default for the stairs mode.
Why does the calculator add 10% by default?
The 10% default protects you from a short pour — a cold joint and a second trip cost more than a little extra concrete. Stairs use 15% because complex forming loses more material to bulkheads and the bottom riser. You can switch it off with the waste toggle if your measurements are exact.

Receipts

Sources & methodology

Pinned sources

Tool-specific choices behind these numbers

The solid-pour stair model
A stair poured against ground or form boards fills the full prism below the treads — not just the visible step blocks. Mathematically a stair with n steps is a stack of rectangular slabs whose heights run 1, 2, … n step-heights from the bottom; the total is W · R · T · n(n+1)/2. That n(n+1)/2 term is why concrete grows faster than linearly with step count: doubling from four to eight steps quadruples the contribution. Some calculators use a per-block shortcut n · W · R · T that roughly halves the true volume — useful for sketching, dangerously low for ordering. We default to the solid model because it matches what most contractors actually pour; an open-riser or sloped-slab stair uses less, and your real order will run lower.
Why round uses π · (D ÷ 2)²
Circle area is π × radius², and the radius is the diameter halved — so the area equals π · (D ÷ 2)². We chose diameter rather than radius because that is the dimension on tube specs and slab drawings. A 10-foot round pad covers about 78.5 sq ft vs 100 for the bounding 10 × 10 square — round consistently uses roughly 21% less concrete than the square that encloses it. If your design has rounded corners on an otherwise square pad, the square calculation overshoots by a small fraction; that overshoot is well within the 10% waste buffer.
Why the cost figure is a static NRMCA-anchored range
Ready-mix concrete is regional and volatile: prices vary by quarry distance, mix spec, short-load surcharges, and season far more than a single national average can capture. The page anchors to the NRMCA 2024 figure of $179.89/yd³ and shows a 2026 range of $160–195 for typical regional and seasonal variation. We round to ~$10 increments because a quote to the cent would imply confidence the data does not support. Live escalation against the BLS PCU327320327320 series earns its keep in the Concrete Slab Cost Calculator, where labor and fees combine into an installed number worth pinning to FRED. Here a static range is the honest tool — and you can always override it with your own delivered quote.
Compute, never copy
Every number on this page traces to a primary source or to geometry. Volume formulas are exact (geometry); bag yields are the QUIKRETE 4000 psi manufacturer spec corroborated by Cemex; density is ACI normal-weight at 150 lb/ft³, the value structural engineers use; cost is anchored to NRMCA, not scraped from a competitor. We do not paraphrase ConcreteNetwork, Homewyse, Angi, or HomeGuide — their numbers are themselves derived, and resurfacing them under a new label would both violate their terms and add no information for you.
The waste convention
A slab or footing is poured roughly horizontal; wastage comes from spillage at the corners, over-excavation, and small measurement errors. Ten percent covers that on a level subgrade and is the default for slabs, round slabs, footings, columns and walls. Stairs are different — forming complex stepped shapes loses more material at the bulkheads and to the slope correction at the bottom riser. Fifteen percent is the contractor convention for poured stairs, and the calculator raises the default to 15% automatically. You can turn waste off entirely, but doing so is rarely worth saving the small material cost — the cold-joint risk on a short pour is the real consequence.
Bag count is off the order volume
The bag count uses the post-waste volume — the order volume — because that is what you actually need to carry, mix and place on site. Counting bags off the pre-waste volume would consistently undercount real-world purchases. The calculator rounds up to whole bags so you never finish a pour one bag short.
Unit conversion uses definitional ratios
Every length you enter converts through the exact identities 1 ft = 0.3048 m and 1 in = 2.54 cm. Switching the calculator from imperial to metric and back leaves the underlying physical size unchanged at machine precision, so a 12-foot slab is the same pour whether you typed twelve feet or its 3.658-meter equivalent. The cubic-yard result is identical to the bit.

For the shared principles — the “real ≠ right” rule we apply to every PPI / USGS / ASTM identifier, the primary-source standard, and the publish-our-receipts approach behind every figure on the site — see the methodology page.

Spot a number that looks off? Email info@constructioncalc.org with the page URL and what you saw — we publish a fix as soon as the underlying source can be confirmed.
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