While you’re repairing foundation walls, paving a driveway or building a sidewalk; you need ready-mix concrete bags. There’re different sizes of bags available like 40 lbs, 60 lbs, 80 lbs and 90 lbs (on the basis of weight). But before buying ready-mix concrete bag, you might be interested to know how much does a bag of concrete cover or how much does one bag of concrete cover.
So, at first you need to determine what size of your driveway or floor slab is and on that basis you can estimate the quantity of concrete required (probably in cubage). You can divide the total volume with the volume of 1 bag of ready-mix concrete to get the total number of bags of concrete required.
Similarly your number of concrete bags per yard will depend on the size of the bag you purchase. There’s no big difference in terms of brand but it’s actually the size of concrete bag that matters.
Ready-mix Concrete bags
A ready-mix concrete bag has a mixture of cement, sand and coarse aggregate mixed in suitable proportion with or without suitable admixtures to get the required strength. Concrete is used as a building material in construction sector because of its large benefits such as
- High Strength
- Durability
- Good Fire resistance
- Economy
- Easy Availability of material
Concrete can be manufactured in different ways.
One is buying of individual ingredients of concrete and then batching and mixing of ingredients in required proportion according to required strength. In other method ready mix concrete is available in market both in dry and plastic state.
Different manufacturers produce concrete in batching plants and then deliver to the construction sites. It is also available in market in dry ready-mix form in bags of different size and weight conditions such as 40lb, 50lb, 60lb, 80lb and 90lb bag.
Also Read: Concrete Block Calculator – How many blocks you need?
Weight & Density of ready-mix concrete
Weight of dry ready-mix concrete which is available in bags of different size is 133lbs/ft3 which is approximately equal to 2135 kg/m3. The weight of concrete is determined by using the simple density formula which is
Density = Mass/volume
We can also calculate the volume of concrete in bags of different sizes and weight by using the same formula.
As we know that dry mix concrete is available in market in bags of different weights for building repair purposes such as foundation and side walls, damaged part of structural member, steps and ramp.
How to calculate the cubage or volume of concrete required?
In this article we will learn that how we can calculate the volume required for our building construction and repair by calculating the area cover by one bag of concrete of different weight for 3” and 4” thick slab and then we will calculate the number of bags for 1 cubic yard of concrete.
In USA, based on imperial measurement system 1 cubic yard which is a unit of volume is equal to 27 ft3.
For easy understanding we can write it as 3ft long, 3 ft wide and 3ft thick and by multiplying we get 27ft3 volume.
Now we will calculate the area cover by 1 bag of concrete of different size for 4” thick slab and number of bags of different size required for 27ft3 of concrete.
Also read: How much is a yard of concrete? – With Bonus tips to save money
How much does one bag of concrete cover?
The coverage for one bag of concrete depends on the thickness of the slab as well as the size of the concrete bag. More the size of the concrete bag and less the thickness more will be the area covered. Here’s how you can calculate the coverage area of concrete bag in square feet.
A bag of concrete covers area (square feet) = (Size of concrete bag x 12 ) / (133 x thickness of slab)
Where size of bag is in lbs. whereas the thickness of the slab is in inches;
A 90 pounds bag of concrete cover 2.06 square feet with a slab of 4 inches thick. A 40 pound bag of concrete would cover 1 square feet. So on average a sack or bag of concrete can cover 1 to 2 square feet if the slab is 4 inches thick.
Also Read: Concrete Topping – Definition, Applications, Types, Advantages and Disadvantages
How much does a bag of 90lbs bag of concrete cover?
A 90lbs bag of concrete yields approximately 0.68ft3. The area that will be covered by 90lbs bag of concrete for 4” thick slab will be 2.06ft2. The number of bags that will be required for 27ft3 of concrete will be 40 and it will cover an area of 81 ft2 for 4” thick slab.
Weight of bag = 90lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete= 0.68ft3
Thickness of slab=4” or 0.33ft
Area covered by 90 lbs bag for 4” inch thick concrete slab=0.68ft3/0.33ft
Area covered by 1 bag (90lbs) of concrete=2.06ft2
Also Read: Sand Blasting Concrete Finish – Purpose, Process, Pros & Cons
Number of 90 lbs bag of concrete for 27 ft3 volume
Weight of bag = 90lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete= 0.68ft3
Total volume of concrete required = 27 ft3
Number of 90lbs concrete bags required=27ft3/0.68ft3
Number of 90lbs concrete bag = 40
How much does a bag of 80 lbs bag of concrete cover?
The volume of concrete in 80lbs bag is 0. 60ft3.The area covered by 80lbs bag for 4” thick slab is approximately 1.82ft2. The number of 80lbs bags which are required for 27ft3 of concrete are 45 and it will cover slab area of 81ft2 with 4” thickness.
Weight of bag = 80lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete= 0.60ft3
Thickness of slab=4” or 0.33ft
Area covered by 80 lbs bag for 4” inch thick concrete slab=0.60ft3/0.33ft
Area covered by 1 bag of concrete=1.82ft2
Number of 80 lbs bag of concrete for 27 ft3 volume
Weight of bag = 80lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete= 0.60ft3
Total volume of concrete required = 27 ft3
Number of 80lbs concrete bags required=27ft3/0.60ft3
Number of 80lbs concrete bag = 45
How much does a bag of 60 lbs bag of concrete cover?
A 60lbs bag of concrete yields approximately 0.45ft3. The area for concrete covered by one 60lbs bag for 4” thick slab will be 1.36ft2. The number of bags that will be required for 27ft3 of concrete will be 60 and it will cover an area of 81 ft2 for 4” thick slab.
Weight of bag = 60lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete= 60lbs/133lb/ft3
Volume of 1 bag of concrete= 0.45ft3
Thickness of slab=4” or 0.33ft
Area covered by 60 lbs bag for 4” inch thick concrete slab=0.45ft3/0.33ft
Area covered by 1 bag of concrete=1.36ft2
Number of 60 lbs bag of concrete for 27 ft3 volume
Weight of bag = 60lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete=60lbs/133lb/ft3
Volume of 1 bag of concrete=0.45ft3
Total volume of concrete required = 27 ft3
Number of 60lbs concrete bags required=27ft3/0.45ft3
Number of 60lbs concrete bag = 60
How much does a bag of a 50 lbs bag of concrete cover?
The volume of concrete in 50lbs bag is 0. 37ft3.The area covered by 80lbs bag for 4” thick slab is approximately 1.12ft2. The number of 50lbs bags which are required for 27ft3 of concrete are 73 and it will cover slab area of 81ft2 with 4” thickness.
Weight of bag = 50lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete= 50lbs/133lb/ft3
Volume of 1 bag of concrete= 0.37ft3
Thickness of slab=4” or 0.33ft
Area covered by 50 lbs bag for 4” inch thick concrete slab=0.37ft3/0.33ft
Area covered by 1 bag of concrete=1.12ft2
Also Read: 9 Types of Concrete Cracks (With Pictures)- Tricks to Prevent – PDF
Number of 50 lbs bag of concrete for 27 ft3 volume
Weight of bag = 50lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete=50lbs/133lb/ft3
Volume of 1 bag of concrete=0.37ft3
Total volume of concrete required = 27 ft3
Number of 50lbs concrete bags required=27ft3/0.37ft3
Number of 50lbs concrete bag = 73
How much does a bag of a 40 lbs bag of concrete cover?
A 40lbs bag of concrete yields approximately 0.3ft3. The area covered by one 40lbs bag of concrete for 4” thick slab will be 0.9ft2. The number of bags that will be required for 27ft3 of concrete will be 90 and it will cover an area of 81 ft2 for 4” thick slab.
Weight of bag = 40lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete= 40lbs/133lb/ft3
Volume of 1 bag of concrete= 0.3ft3
Thickness of slab=4” or 0.33ft
Area covered by 40 lbs bag for 4” inch thick concrete slab=0.30ft3/0.33ft
Area covered by 1 bag of concrete=0.9ft2
Number of 40 lbs bag of concrete required for one yard
Weight of bag = 40lbs
Density of bag of concrete=133lb/ft3
Volume of 1 bag of concrete=40lbs/133lb/ft3
Volume of 1 bag of concrete=0.30ft3
Total volume of concrete required = 27 ft3
Number of 40lbs concrete bags required=27ft3/0.30ft3
Number of 40lbs concrete bag = 90
| Size of Bag (lbs) | Volume of 1 bag (ft3) | |||||||||
| 4 | 5 | 6 | 7 | 8 | ||||||
| 90 | 0.68 | 2.04 | 1.63 | 1.36 | 1.17 | 1.02 | ||||
| 80 | 0.6 | 1.80 | 1.44 | 1.20 | 1.03 | 0.90 | ||||
| 60 | 0.45 | 1.35 | 1.08 | 0.90 | 0.77 | 0.68 | ||||
| 50 | 0.37 | 1.11 | 0.89 | 0.74 | 0.63 | 0.56 | ||||
| 40 | 0.3 | 0.90 | 0.72 | 0.60 | 0.51 | 0.45 | ||||
How many bags of concrete for 1 cubic yard
| Size of Bag (lbs) | No of bags required for cubic yard of concrete |
| 1 | |
| 90 | 40 |
| 80 | 45 |
| 60 | 60 |
| 50 | 73 |
| 40 | 90 |
Estimating your concrete requirements
If you’re pouring a slab or are paving concrete with near-to-uniform thickness that means you’re more interested in dealing with unit of area rather than cubage.
Let’s say you have a an area of about 350 square foot and you want to pour a patio concrete slab of 4 inches thick, you want to know how many 90lbs size concrete bags you need to cover the area of your patio.
If you don’t have area measurement, it’s easy to takeoff measurements using a simple measuring tape. Just know the far ends of the patio slab and take linear measurements i.e. length and width.
If you’re area is not irregular you can easily divide it into rectangles and triangles and at the end make a summation of the entire area.
Also Read: Gypcrete Vs Concrete – Difference – Composition – Uses – Pros & Cons
A gift
I have designed an excel sheet that will take care of all of your ready-mix concrete estimation problem. In that calculator, you just choose the size of the concrete bag, enter the thickness of the slab and it will tell you how much area the concrete bag will cover.
You can divide your total area with the area above to get the total number of bags required.
In the same calculator, I’ve also added a feature to know no of bags of concrete per cubic yard of concrete. So, if you have estimated the concrete required per cubic yard you can easily know the no of bags of concrete required depending on the size of bag you choose and the cubic yard of concrete you enter.
You can download the excel sheet for free of cost.
