Construction & Materials

Quikrete Calculator

Bags needed

Cubic yards

Cost estimate

Project DimensionsFree - Instant

Length (ft)

Width (ft)

Depth (inches)

Cost per bag ($)

Bag Size

How Quikrete Bags Are Calculated

The volume of concrete needed is length times width times depth (all in feet). Dividing by the cubic footage per bag gives the number of bags. Always round up and order 5-10% extra for waste.

Volume (cu ft) = Length x Width x (Depth in / 12)
Bags = ceil(Volume / cu ft per bag)
80 lb bag = 0.6 cu ft, 60 lb = 0.45, 40 lb = 0.3

Who Is This Calculator For?

Anyone mixing or ordering bags of Quikrete or similar pre-mixed concrete for a DIY or professional project.

Homeowners setting fence posts

Know exactly how many 60 or 80 lb bags to buy before digging so you don't run short mid-project.

DIYers pouring a concrete slab

Calculate bags for a patio, sidewalk, or garden pad without over-ordering and wasting money.

Landscapers installing pavers

Estimate concrete for setting border stones, stepping stones, or precast edging in a single trip.

Contractors pricing small pours

Get a quick bag count and cost estimate to include in a job quote for a customer.

Handymen repairing steps or footings

Find the cubic footage of a broken section and buy only what you need to patch it.

Builders setting mailbox or sign posts

Determine how many bags are required per post hole to ensure a solid, frost-resistant base.

When Should You Use It?

Before going to the hardware store so you buy the right number of bags in one trip
When switching between 40 lb, 60 lb, and 80 lb bag sizes to compare total cost
To confirm your project is small enough for bagged concrete rather than a ready-mix truck
When planning multiple post holes on the same day to total up all bags needed
Any time your project area is not a standard shape and you need to verify the math

Example Calculations

Example 1: 10x10 backyard patio at 4 inches deep

A homeowner wants to pour a 10 ft x 10 ft concrete pad at 4 inches deep for a shed base.

Volume = 10 x 10 x (4/12) = 33.3 cu ft
80 lb bags (0.6 cu ft each): ceil(33.3 / 0.6) = 56 bags
60 lb bags (0.45 cu ft each): ceil(33.3 / 0.45) = 74 bags
Cost at $8/bag (80 lb): 56 x $8 = $448

Example 2: Three fence posts at 10 inches wide x 36 inches deep

Installing 3 fence posts in holes that are 10 inches in diameter and 36 inches deep.

One hole: (10/12) x (10/12) x (36/12) = 2.08 cu ft
Three holes: 2.08 x 3 = 6.25 cu ft
60 lb bags needed: ceil(6.25 / 0.45) = 14 bags

Common Mistakes to Avoid

Entering depth in feet instead of inches

The depth field expects inches. If your slab is 4 inches deep and you type 4, that is correct. If you type 0.33 (the foot equivalent) the result will be drastically underestimated. Always use inches for depth.

Forgetting to add a waste buffer

The calculator gives the theoretical volume. Real pours lose 5-10% to spillage, uneven sub-grade, and air voids. Buy at least one extra bag per 10 bags calculated, or round up to the nearest case.

Using the wrong depth for the project type

Residential foot traffic slabs need 4 inches; driveways need 4-6 inches; fence posts need to go below the frost line (36+ inches in cold climates). Using the wrong depth produces a dangerously under-built pour.

Confusing Quikrete Fast-Set with standard mix for large slabs

Fast-Setting Concrete sets in 20-40 minutes. For pours larger than a few square feet, you will not have time to screed and finish before it hardens. Use standard mix for slabs and save Fast-Set for post holes.

Not compacting the sub-base first

Pouring concrete over loose or unprepared soil leads to cracking and settling. Compact 4 inches of gravel base material before any slab pour. The calculator result assumes correct sub-base preparation.

Frequently Asked Questions

A 10x10 foot slab at 4 inches deep is 33.3 cubic feet. Each 80 lb bag of Quikrete covers 0.6 cubic feet, so you need 56 bags. At 3.5 inches, you would need 49 bags. Always add 5-10% extra to account for spillage and uneven sub-grade.

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Sources & References

Quikrete Companies - Product Data Sheets

Source for bag coverage figures: 80 lb = 0.6 cu ft, 60 lb = 0.45 cu ft, 40 lb = 0.3 cu ft of mixed concrete per bag.

ACI 318-19 Building Code Requirements for Structural Concrete

Source for minimum slab thickness recommendations: 4 inches for residential foot traffic, 6 inches for driveways supporting vehicles.

International Residential Code (IRC) - Section R403 Footings

Source for footing depth requirements and frost line guidance used in the fence post depth recommendation (36+ inches in cold climates).

Hassaan Rasheed

Developer and Researcher, CalculatorFlux

Researches and verifies the formulas, methodology, and source data behind each calculator on CalculatorFlux. All tools are built and checked against the cited references before publication.

Last updated: May 2026

Bag Coverage Reference

Bag Size	Coverage
40 lb bag	0.3 cu ft
50 lb bag	0.375 cu ft
60 lb bag	0.45 cu ft
80 lb bag	0.6 cu ft

Pro Tip

For projects over 1 cubic yard (27 cu ft), ordering ready-mix concrete delivered by truck is almost always cheaper than buying bags. A standard ready-mix truck delivers 8-10 cubic yards per load.

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