Quick start
- Enter the total footing length in feet.
- Enter width and depth in inches because footing cross-sections are often measured that way.
- Add waste for uneven trench bottoms, overdigging, spillage, and a small ordering cushion.
Best uses
Best for straight rectangular footing runs where the width and depth are already known and you need concrete volume or bag planning.
- Estimate concrete for a simple straight footing run.
- Convert width and depth in inches into cubic yards.
- Compare ready-mix volume with common bag counts.
- Add a realistic waste cushion before pricing material.
What this calculator is solving
The Concrete Footing Calculator estimates concrete for a straight rectangular footing. It is a material helper after you already know the footing size.
Match each input label on the calculator to the straight footing run, planned footing width, planned footing depth, and waste cushion from your drawing, permit notes, or contractor plan.
The formula in plain language
In plain language: The calculator converts footing width and depth from inches to feet, multiplies length by width by depth, adds the waste percent, converts cubic feet to cubic yards, and rounds 60 lb and 80 lb bag counts up. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.
For example, a 30 ft footing that is 16 in wide and 8 in deep is 30 x 1.333 x 0.667 = about 26.67 cubic feet before waste. With 10% waste, it becomes 29.33 cubic feet, or about 1.09 cubic yards.
How to read the answer
Use cubic yards when you are asking for ready-mix pricing. Use 60 lb or 80 lb bag counts only for small hand-mixed jobs because footings get heavy quickly.
- Cubic yards is the ready-mix style volume.
- Cubic feet shows the smaller volume unit before converting to yards.
- 60 lb and 80 lb bag counts are rounded up for small bagged-concrete jobs.
- Bag counts are material estimates, not a promise that hand-mixing is the best way to pour a long footing.
Common mistakes to avoid
The easy mistake is using the calculator to pick the footing size. It only estimates concrete after the width and depth are already decided.
- Do not use the calculator to choose the footing size.
- Do not ignore frost depth, soil bearing, reinforcement, drainage, inspections, or local code.
- Do not forget that trench overdigging can increase concrete volume.
- Do not include slab, pier, column, or wall concrete unless you calculate those parts separately.
Quick footing example
Say a footing run is 30 feet long, 16 inches wide, and 8 inches deep. Convert width and depth to feet first: 16 inches is 1.333 feet, and 8 inches is 0.667 feet.
The raw volume is about 26.67 cubic feet. With 10% waste, the calculator shows about 29.33 cubic feet, 1.09 cubic yards, 49 eighty-pound bags, or 66 sixty-pound bags.
Why cubic yards matter
Ready-mix concrete is usually discussed in cubic yards. Bag counts are useful for small repairs, but a long footing can turn into dozens or hundreds of bags.
Use the bag count as a reality check. If the number looks huge, a supplier quote may be safer and less exhausting than hand mixing.
Cost checks without guessing
The page does not invent a concrete price because local ready-mix, short-load fees, delivery, taxes, forms, rebar, labor, and tools can change the real cost.
Use the cubic-yard result for supplier calls, or multiply the rounded bag count by your store price for a rough material-only check.
What this does not design
Footing width and depth are safety choices, not just calculator inputs. They can depend on loads, soil bearing value, frost protection, slope, drainage, reinforcement, and inspections.
The 2024 IRC foundation chapter ties footing width and thickness to foundation tables and soil load-bearing values, so check local rules or a qualified professional before relying on a footing size.
Research and references
These references help check concrete volume math, bag-yield context, foundation safety limits, and unit conversions.
Worked examples for Concrete Footing Calculator
29.33 ft3, about 1.09 yd3, 49 eighty-pound bags
12.96 ft3, about 0.48 yd3, 22 eighty-pound bags
3.5 ft3, about 0.13 yd3, 6 eighty-pound bags
91.67 ft3, about 3.4 yd3
FAQ in plain language
When should I use the Concrete Footing Calculator?
Use it when your task matches one of these common needs: Estimate concrete for a simple straight footing run. Convert width and depth in inches into cubic yards. It works best when you already know the measurements, amounts, units, or options the page asks for.
What is the Concrete Footing Calculator doing with my inputs?
In plain language: The calculator converts footing width and depth from inches to feet, multiplies length by width by depth, adds the waste percent, converts cubic feet to cubic yards, and rounds 60 lb and 80 lb bag counts up. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.
What do the main Concrete Footing Calculator inputs mean?
Footing length: the total straight run of the footing in feet. Footing width: the planned cross-section width in inches, not the wall width unless they match your drawing. Footing depth: the planned concrete thickness in inches. Waste percent: extra concrete for uneven trench bottoms, overdigging, spillage, and a small ordering cushion. Bag counts: rounded estimates using common dry-mix yields, useful for small hand-mixed jobs.
How should I read the Concrete Footing Calculator answer?
Read the headline estimate first, then check the material, waste, coverage, and unit lines. For project tools, the supporting lines are often the difference between a rough idea and a list you can actually shop from.
What should I double-check before trusting the answer?
This estimates concrete material after you already know the footing size. Soil bearing, loads, frost depth, reinforcement, drainage, slope, forms, inspections, and local code can change the real footing design. Also check the unit, scale, mode, and result limit because small input changes can change the answer.
Why does the Concrete Footing Calculator show both cubic yards and bags?
Cubic yards are useful for ready-mix orders, while 60 lb and 80 lb bag counts are useful for smaller hand-mixed projects. Large footings are usually better handled with a concrete supplier or contractor.
How do I calculate concrete for a footing?
Convert width and depth from inches to feet, multiply length x width x depth, add waste, then divide cubic feet by 27 to get cubic yards.
Related tools
- Concrete CalculatorEstimate slab volume, cubic yards, cubic meters, and common 40, 60, and 80 lb bag counts.
- Rebar CalculatorEstimate rebar grid counts, linear feet, and stock bars from slab size and spacing.
- Cubic Yard CalculatorConvert length, width, depth, and waste into cubic feet and cubic yards.
- Concrete Column CalculatorEstimate concrete for round columns, piers, and tube forms.
Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Home & ProjectsBrowse the full category for related tools that help with the same job.
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- All calculator and utility guidesFind more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resourcesStart here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.