Answer

Estimated Concrete Volume

3.5 cubic yards

94.5 cubic feet

Estimated Weight of Concrete

## 6.28 tons

Covering 189 sq. ft. at 6" depthChange dimensions

Optional 10% extra concrete

for waste allowance

10% = 0.35 cubic yards

Total Concrete with 10% = 3.85 cubic yards

for waste allowance

10% = 0.35 cubic yards

Total Concrete with 10% = 3.85 cubic yards

## Order Size

This order size is considered

**Large**### How Many Concrete Bags?*

210 | 60lb Concrete bags |

158 | 80lb Concrete bags |

47.3 | Small wheelbarrow loads |

23.6 | Large wheelbarrow loads |

## Concrete Truck for 9'x21' x6"

35%

**0.35 Concrete Truck Loads**(10 cu/yd Capacity)

## Cost Estimate for 9'x21' x6"

Purchasing ready-mix concrete is by far the easiest way to mix concrete for medium to large projects and can even be used on smaller projects as well. We have provided a cost comparison between ready mix and DIY concrete premix bags to give you a rough ballpark estimate.

## Bag Cost Estimate

Pre-mixed concrete bags cost on average $3.50 per 80lb bag. Using pre-mixed bags to cover 189 sq ft at a depth of 6", the estimated cost is

**$553.00****$553.00**

for 158 x 80lb bags

## Truck Cost Estimate

Ready-mixed concrete costs on average $108.22 per cubic yard delivered. Using a concrete truck to cover 189 sq ft at a depth of 6", the estimated cost is

6.5 x $17.00 = $110.50

$378.77 + $110.50 =

*6 inch pours and under.

**Cost assumes subbase and general prep is done.

**$378.77**Concrete trucks may also charge a **"short load"** fee for partially filled loads. Short load fees are charged at about $17 for every yard not used on the truck.

6.5 x $17.00 = $110.50

$378.77 + $110.50 =

**$489.27****$489.27**

### Pros Do Everything*

$945.00 | $5.00 sq ft Low End** |

$1,134.00 | $6.00 sq ft |

$1,323.00 | $7.00 sq ft |

$1,512.00 | $8.00 sq ft |

$1,984.50 | $10.50 sq ft High End*** |

*6 inch pours and under.

**Cost assumes subbase and general prep is done.

## Concrete Extras

A well-compacted

**subbase**provides a strong foundation for concrete to lay on. We recommend you contact your nearest concrete supplier for their recommendations on whether you need a subbase, base depth, and rock type.With a brief look, a 9x21 area at 6 inches deep, you would need approximately **4.97 tons** or **3.5 cubic yards of gravel**.

**Concrete reinforcing** is also recommended in high traffic areas and medium to large areas. **Wire mesh** on average costs **$0.56 per sq ft** and **fiber mesh** costs **$0.13 per sq ft**.

So for your **189 sq ft area**, this may roughly cost **$105.84** for wire mesh, **$567.00** for thicker wire rebar mesh and **$24.57** for fiber mesh.

How to Calculate Concrete Amount for 9x21 x6"

9 * 21 = 189 sq ft

6 / 12 = 0.5 ft depth

189 * 0.5 = 94.5 cu ft

94.5 / 27 = 3.5

= 3.5 cu/yd

How to Calculate Concrete Weight

3.5 * 3590 = 12565 lbs

Density of concrete used 2130 kg/m

6 / 12 = 0.5 ft depth

189 * 0.5 = 94.5 cu ft

94.5 / 27 = 3.5

= 3.5 cu/yd

How to Calculate Concrete Weight

3.5 * 3590 = 12565 lbs

Density of concrete used 2130 kg/m

^{3}or 133 lbs/ft^{3}.## 9 ft x 21 ft x 6" Concrete Summary

**How much concrete do I need for an area of 9 ft x 21 ft x 6" depth?**3.5 cu. yds.

**How many concrete bags would I need for a 9 ft x 21 ft x 6" slab?**158 x 80lb Concrete bags.

**How much does it cost to pour a 9'x21' x6" slab?**Ready-mix costs approx $489.27.

**How much does it cost to hire a contractor to concrete a 9'x21' x6" slab?**A pro costs between $945.00 and $1,984.50.

**How do you calculate concrete volume?**Formula ((width x length) x (depth in inches / 12)) / 27 = total cubic yards. See our how to here

**This Page is Calculated for the Following:**9 ft x 21 ft x 6", 9x21x6, 189 sq. ft., 9 x 21, 9x21, 9x21 x6", 9'

*x*21'

*x*6", 9'x21' x6"

This

**Concrete**calculator can be used for a slab, floor, garage, block, wall, driveway, patio, countertop, footings, foundation, pool or basement, and most rectangular areas.