Concrete Calculator
Slabs, footings, columns, post holes, and steps, in cubic yards and bags, with a bags versus ready-mix check.
Quick answer
One cubic yard of concrete is 45 bags of 80 lb, 60 bags of 60 lb, or 90 bags of 40 lb. A 10 x 10 ft slab 4 inches thick needs about 1.23 cubic yards, or 56 bags of 80 lb, before extra for waste.
What are you pouring?
5 to 10% covers uneven ground and spills
What goes with it
18 to 24 in on center is common
Adds a frost-depth reminder and goes into your copied order.
1.36 cubic yards of concrete, or 62 bags of 80 lb.
You need
1.36cubic yards
= 36.7 cu ft, including 10% extra · weighs about 5,500 lb poured
10 x 10 ft slab, 4 in thick
| Bag size | Bags | Total weight |
|---|---|---|
| 90 lb bag (0.675 cu ft) | 55 | 4,950 lb |
| 80 lb bag (0.60 cu ft) | 62 | 4,960 lb |
| 60 lb bag (0.45 cu ft) | 82 | 4,920 lb |
| 50 lb bag (0.375 cu ft) | 98 | 4,900 lb |
| 40 lb bag (0.30 cu ft) | 123 | 4,920 lb |
HaulOnce order ticket
Concrete order
Ticket no.
373856
Option A: Bags
Cheaper62 bags
Example price, enter yours
Option B: Ready-mix
1.5 cu yd
Rounded up to the nearest 0.25 yd.
Example, enter yours
Often included
Example, ask the plant
This order is under the short-load threshold, so the fee is included.
Ready-mix is cheaper above 1.4 cu yd. Bags saves $25.50 here.
Bags mean lifting 62 bags, 4,960 lb of dry mix, then mixing every one before the first sets. Past about a yard, most people order a truck.
Also on the list
Estimate from haulonce.com. Weights vary with moisture and supplier. Prices are examples unless you entered your own.
Haul Check
Typical 1,500 to 2,300 lb. We use the low end until you enter yours.
Check the Tire and Loading Information sticker on your driver's door jamb for your exact payload.
Bagged concrete hits your payload long before your bed is full.
That is 3,460 lb over your payload. You need 4 trips.
Split it into 4 loads of about 0.34 cu yd (1,240 lb) each, or get it delivered instead. At this many trips, delivery usually costs less than your time and fuel.
Using the low end of the typical payload range. Enter your own for an exact answer.
This checks hauling the bags yourself. Ready-mix arrives in the plant's truck.
What pros know
- An 80 lb bag yields about 0.6 cu ft, so a full cubic yard is 45 bags and 3,600 lb of dry mix to lift. Source
- Every bag size works out to the same 3,600 lb of dry mix per cubic yard. Smaller bags are easier to lift, not lighter in total. Source
- Set posts in a hole about 3 times the post's width, dug to about one third of the post's total length. Source
Ready to text or email your supplier:
“I'm picking up 62 bags of concrete mix (80 lb).”
Add your ZIP code above to include it.
What did you pay? (optional)
How the calculator works
Pick the shape you are pouring. Slabs and footings are length x width x depth. Columns and Sonotubes are circles times height. Post holes are the hole minus the post, filled to a few inches below grade. Steps are counted as solid blocks: the bottom step is one riser tall, the next is two, and so on, plus any landing on top.
Volume is converted to cubic yards (27 cubic feet each), extra is added for waste, and the total is rounded up to whole bags in every size and to the nearest 0.25 yard for a ready-mix order.
How many bags of concrete per yard
| Bag size | Yield per bag | Bags per cu yd | Bags for a 10 x 10 ft slab, 4 in |
|---|---|---|---|
| 90 lb bag | 0.675 cu ft | 40 | 50 |
| 80 lb bag | 0.6 cu ft | 45 | 56 |
| 60 lb bag | 0.45 cu ft | 60 | 75 |
| 50 lb bag | 0.375 cu ft | 72 | 89 |
| 40 lb bag | 0.3 cu ft | 90 | 112 |
Yields from the QUIKRETE Concrete Mix data sheet, before any extra for waste. Other brands are similar; check the bag.
Concrete for fence posts
QUIKRETE's guidance is a hole about 3 times the width of the post, dug to about one third of the post's total length. A 4x4 (3.5 in actual) wants roughly a 10 to 12 in hole; an 8 ft post goes about 32 in deep. Where the ground freezes, go below the frost line.
Their own example: two 50 lb bags of Fast-Setting Concrete set a 4 in post in a 10 in hole 2 ft deep. The calculator fills to about 3.5 in below grade and rounds up, so it may suggest one more bag than that. Leftover bags are easy to return.
Weight and hauling
Poured concrete weighs about 4,050 lb per cubic yard, roughly 150 lb per cubic foot. The dry mix in bags works out to 3,600 lb per yard in every bag size: 45 bags of 80 lb, or 90 bags of 40 lb, is the same weight.
A full-size half-ton pickup typically carries 1,500 to 2,300 lb, so one yard of bags is often two trips, and that is before you lift every bag twice. The Haul Check in the calculator works it out for your vehicle. Your exact payload is on the driver's door-jamb sticker.
Bags or a ready-mix truck
Bags make sense for post holes, small pads, and repairs. Past about a cubic yard, mixing becomes the problem: every bag has to be mixed and placed before the first one starts to set, which is hard for one or two people. Ready-mix arrives mixed, but plants often charge a short-load fee on small orders (commonly under about 4 yards; ask yours).
Enter your own bag price, ready-mix price, delivery fee, and short-load fee in the Order Ticket, and it shows the exact size where ready-mix becomes cheaper. The defaults are example prices, not local quotes.
What pros know
- An 80 lb bag yields about 0.6 cu ft, so a full cubic yard is 45 bags and 3,600 lb of dry mix to lift. (QUIKRETE)
- Every bag size works out to the same 3,600 lb of dry mix per cubic yard. Smaller bags are easier to lift, not lighter in total. (QUIKRETE)
- Set posts in a hole about 3 times the post's width, dug to about one third of the post's total length. (QUIKRETE)
Common mistakes
- Ordering the exact volume. Uneven ground eats concrete; add 5 to 10 percent.
- Mixing bags by hand for a full yard. Past about 40 bags, rent a mixer or call a truck.
- Forgetting the short-load fee on small ready-mix orders.
- Setting posts above the frost line in cold climates, where they heave.
- Loading a yard of bags into a half-ton pickup in one trip.
Questions people ask
How many bags of concrete do I need?
Work out cubic feet (length x width x depth in feet), then divide by the bag yield: 0.60 cu ft for 80 lb, 0.45 for 60 lb, 0.30 for 40 lb. One cubic yard is 45 bags of 80 lb. Add 5 to 10 percent for waste.
How many 80 lb bags of concrete are in a yard?
45. Each 80 lb bag yields about 0.60 cubic feet, and a cubic yard is 27 cubic feet.
How much concrete do I need for a fence post?
It depends on hole size and depth. As a reference, QUIKRETE says two 50 lb bags of Fast-Setting Concrete set a 4 in post in a 10 in hole 2 ft deep. Use the Post holes option above for your posts.
How much does a yard of concrete weigh?
About 4,050 lb poured, roughly 2 tons. The dry mix in bags for one yard is about 3,600 lb.
Is it cheaper to buy bags or ready-mix concrete?
For small jobs, bags. For larger pours, ready-mix usually wins once the short-load fee is spread over enough yards. Enter your prices in the calculator to see the exact crossover.
How much concrete do I need for a Sonotube?
Multiply the circle area by the height: a 12 in tube 4 ft tall is about 3.14 cubic feet, or 6 bags of 80 lb. Use the Column option above for several tubes.
Sources
- QUIKRETE, Concrete Mix No. 1101 data sheet (bag yields, post setting method)
- QUIKRETE, Fast-Setting Concrete Mix spec data sheet (post setting yields)
- The Engineering ToolBox, Dirt and Mud: Densities (dry, moist, and wet soils, sand, and gravel)
- NHTSA, Tires: the Tire and Loading Information placard on the driver's door jamb
Last reviewed: . How we calculate
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