Concrete Bag Calculator
This concrete bag calculator answers how many bags of concrete you need for a slab, pad, or post holes. Enter the dimensions or the volume and the bag size, and the concrete bag calculator returns the number of 40, 60, or 80 lb premixed bags, such as Quikrete or Sakrete, with a waste allowance.
Results
The Concrete Bag Calculator is part of our Concrete collection. Browse more concrete to size, convert, and check your work alongside this tool.
What the concrete bag calculator shows
Premixed concrete bags are sold by weight, but each weight fills a set volume: an 80 lb bag yields about 0.60 cubic feet, a 60 lb bag 0.45, and a 40 lb bag 0.30. The concrete bag calculator divides your volume by the bag yield and rounds up, and shows the count for all three bag sizes so you can compare.
Cubic feet to bags of concrete
Dimensions in metres are converted to cubic feet first (1 m³ = 35.31 ft³). The result is always rounded up to whole bags.
How many bags of concrete do I need: example
A 3 m by 3 m pad, 100 mm thick, with 10 percent waste:
The same pad needs 78 bags of 60 lb or 117 bags of 40 lb. One cubic yard (27 ft³) takes exactly 45 bags of 80 lb.
How to use the sack concrete calculator
Enter the length, width, and thickness of the slab, or enter the volume in cubic feet directly. Choose the bag size and a waste allowance of about 10 percent. The sack concrete calculator returns the bags needed for your size plus the counts for 80, 60, and 40 lb bags. It works for Quikrete, Sakrete, and other premix brands with similar yields.
Reading the bag calculator concrete result
The count is rounded up, so you have a small margin even before waste. Bigger bags mean fewer trips but heavier lifting; 80 lb bags are the most economical per cubic foot. Above about one cubic yard, ready-mix delivery is usually cheaper and faster than mixing bags. Asking how many bags of concrete will I need for a yard has a simple answer: 45 bags of 80 lb, 60 of 60 lb, or 90 of 40 lb.
When to use the quikrete bag estimator
- Setting fence or deck posts with the quikrete bag estimator
- Pouring a small pad, step, or shed base
- Converting cubic feet to bags of concrete
- Deciding between bags and ready-mix
Common concrete bag calculator mistakes
- Confusing cement bags with premixed concrete. Cement alone needs sand and gravel added.
- Forgetting waste.
- Ignoring the post volume in post holes.
Tips for accurate results
- Buy one or two extra bags and return unused ones.
- Use 80 lb bags for the best cost per cubic foot.
- Switch to ready-mix above about one cubic yard.
Quikrete calculator footings and post holes
For post holes, find the hole volume (for a round hole, π × radius² × depth), subtract the post's own volume, and convert to cubic feet; then enter that volume directly. A 10 inch hole 3 feet deep around a 4 by 4 post takes about 1.4 cubic feet, so three 80 lb bags with a little spare. The fence calculator counts the posts for a whole fence line.
Sakrete estimator: does brand matter?
Most premixed concrete brands list similar yields for the same bag weight, so the counts here apply broadly. Check the bag label if a product is a special mix, such as fast-setting or high-strength, as yields can differ slightly.
How many bags of concrete in a yard
How many bags of concrete is a yard? It depends on the bag size. Going the other way, how many yards is a bag of concrete: an 80 lb bag is about 0.022 cubic yards.
| Bag size | Yield per bag | Bags per cubic yard | Bags per m³ |
|---|---|---|---|
| 80 lb | 0.60 ft³ | 45 | 59 |
| 60 lb | 0.45 ft³ | 60 | 79 |
| 40 lb | 0.30 ft³ | 90 | 118 |
Concrete Bag Calculator FAQ
How many 80 lb bags of concrete make a yard?
45 bags, since a cubic yard is 27 cubic feet and each bag yields 0.60 cubic feet.
How many cubic feet is an 80 lb bag of concrete?
About 0.60 cubic feet.
How much waste should I add?
About 10 percent for spillage and uneven forms.
When should I use ready-mix instead of bags?
Usually above about one cubic yard, where delivery is cheaper and faster.