Free Calculator · By SubcontractorHub Editorial Team · Published November 2026
Concrete Footing Calculator for Continuous and Pad Volume
A concrete footing calculator multiplies length, width, and depth, then divides by 27. A continuous run 40 feet long, 16 inches wide, and 8 inches deep is 35.556 cubic feet and 1.317 cubic yards at three decimals. Bags appear only from a yield. The box starts at 0.60 cubic feet because that is the approximate yield of one 80 pound bag on a fetched QUIKRETE sheet. The 16 by 8 inch section is an example, not a code size.
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Book a DemoHow the Concrete Footing Calculator Uses Volume
Continuous runs ignore the pad count. Pads multiply one footing by the count you type.
0.60 is the approximate yield of one 80 pound bag of QUIKRETE Concrete Mix 1101. It is not every bag on the market. 16 by 8 inches is an example size, not a code footing.
35.556 cubic feet = 1.317 cubic yards. Bags at 0.60 cu ft: 59.259, which rounds up to 60 whole bags.
All calculations are estimates based on historical information and should be verified by the user.
Important: no code width was fetched
All calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements.
A Footing Is Not the Whole Concrete Calculator
Slabs, walls of ready-mix, and columns in general are the concrete calculator. This concrete footing calculator stays on two shapes: a continuous trench footing and a repeated pad. Steel in either shape is the rebar calculator, which counts bars and pounds and does not divide by 27. Masonry units are the concrete block calculator.
No building-code minimum width or depth was fetched, so none is printed. Type the width and depth on the drawing or on the local footing table you are actually using. Sixteen inches by eight inches is only the example that makes the division by 12 visible.
The bag yield that was fetched
QUIKRETE Concrete Mix, product number 1101, data sheet revised October 2022 and fetched 2026-11-05, says the mix is for pouring concrete 2 inches thick or more, and the product-use list includes foundation walls and footings. An 80 pound bag yields approximately 0.60 cubic feet. A 60 pound bag yields approximately 0.45 cubic feet. A 40 pound bag yields approximately 0.30 cubic feet. The word on the sheet is approximately. Replace 0.60 when the bag in the truck prints a different yield. Clear the box if you are ordering ready-mix by the yard and do not want a bag count.
The same sheet lists a typical unit weight of about 140 pounds per cubic foot under ASTM C138, and a final water content of about 6 to 9 pints per 80 pound bag. This calculator does not turn 140 pounds per cubic foot into a structural load, and it does not tell you how much water to add. Those lines are on the sheet so the yield is not a mystery number. Follow the bag for mixing.
Worked continuous footing
Length 40 feet. Width 16 inches, which is 1.333 feet. Depth 8 inches, which is 0.667 feet. Cubic feet are 40 times 1.333 times 0.667, which is 35.556 at three decimals. Divide by 27 and the volume is 1.317 cubic yards. At 0.60 cubic feet per bag the bag count is 59.259, which rounds up to 60 whole bags. Order the yards if a truck is coming. Order the bags only if you will actually buy bags of that yield.
| Step | Operation | Example |
|---|---|---|
| To feet | inches ÷ 12 | 16 in = 1.333 ft; 8 in = 0.667 ft |
| Cubic feet | length × width × depth | 35.556 |
| Cubic yards | cubic feet ÷ 27 | 1.317 |
| Bags | cubic feet ÷ yield | 59.259, round up to 60 |
How should you write the footing order?
- Continuous or pad, and the count of pads if you used pads.
- Length in feet, width in inches, depth in inches, labeled as the drawing's sizes.
- Cubic yards at three decimals, before bags.
- Bag yield if you used one, and the product the yield came from. Say 0.60 is approximate.
- Whole bags only after rounding up, and say that you rounded.
- A note that no code minimum width was applied, and that rebar is a separate count.
Pads Multiply One Volume
Switch to pads and the same three dimensions describe one pad. The count multiplies the cubic feet. Four identical pads are four times one pad. Pads that are not identical have to be run separately and added. The tool does not average two different sizes into one pad.
Waste is not built in. If the trench is wider than the form, type the width you will actually fill. Do not expect the page to add a percent. A percent that was not fetched is not hiding in the division by 27.
Ready-mix and bags answer different orders. A yard of truck mix is the cubic-yard line. A Saturday repair with 80 pound bags is the bag line, and only after you confirm the yield on the bag you will buy. QUIKRETE 1101 is one product. Another brand's 80 pound bag is not automatically 0.60 cubic feet.
Frequently Asked Questions
How does the concrete footing calculator get cubic yards?
Multiply length in feet by width in feet by depth in feet, then divide by 27. Width and depth are typed in inches and divided by 12 first. A continuous run 40 feet long, 16 inches wide, and 8 inches deep is 35.556 cubic feet and 1.317 cubic yards at three decimals. Those dimensions are the example. They are not a code minimum.
When does the bag line appear?
Bags equal cubic feet divided by the yield you leave in the box. The box starts at 0.60 cubic feet, the approximate yield of an 80 pound bag of QUIKRETE Concrete Mix number 1101 on the data sheet fetched for this page. Clear the box and the bag line stays blank. Whole bags are that result rounded up.
Is a pad footing the same formula?
Yes, multiplied by the number of pads. Each pad uses its own length, width, and depth. The page does not assume the pads are square unless you type equal sides. Count starts at 1.
Is this the concrete calculator?
No. The concrete calculator is the general pour page for slabs and other shapes. This concrete footing calculator is only continuous runs and pads. Rebar inside the footing is the rebar calculator. Neither page prints a code footing width, because no code width was fetched.
Order Yards First
Cubic yards do not need a bag yield. Bags need the yield on the bag you will buy.
Get a Free DemoAll calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements.