10 ft x 12 ft x 4 in
- Cubic feet
- 44
- Cubic meters
- 1.2459412501
- 80 lb bags
- 74
- 60 lb bags
- 98
Bag counts use common approximate dry-mix yields. Check the exact bag label before buying.
Concrete Calculator
Use this free concrete calculator to estimate slab concrete volume, cubic yards, cubic meters, and common bag counts from length, width, depth, and waste.
Inputs explained Result checks Example values Runs in your browser
Formula steps
- Convert depth from inches to feet.
- Multiply length by width by depth to find cubic feet.
- Add the waste percentage, then divide by 27 for cubic yards.
How to use the Concrete Calculator
- Enter the requested dates, times, grades, dimensions, network values, password options, or units.
- Check the assumptions shown on the page, especially school scales, payroll rules, concrete waste, subnet type, or security handling.
- Press the calculate button to see the answer, supporting metrics, and formula steps.
- Use examples, recent answers, or copy the result while keeping the estimate limits in mind.
What people use it for
Estimate concrete for a simple slab, pad, walkway, or small project.
Convert cubic feet to cubic yards before ordering ready-mix.
Estimate common 40 lb, 60 lb, and 80 lb bag counts.
Add waste percentage before buying materials.
Check whether a project is closer to bagged mix or ready-mix delivery.
Quick examples
10 x 12 slab
10 ft x 12 ft x 4 in, 10% extra1.63 yd3 and 74 80 lb bags
Walkway
24 ft x 3 ft x 4 in, 10% extra0.98 yd3 and 44 80 lb bags
Small pad
6 ft x 6 ft x 3.5 in, 5% extra0.41 yd3 and 19 80 lb bags
Driveway bay
20 ft x 10 ft x 4 in, 10% extra2.72 yd3 and 123 80 lb bags
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the Concrete Calculator See slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- Home & Projects Browse related calculators and utilities in the same category.
- Home Material Calculator Hub Compare this with the nearby tools and checks in the same job path.
- Calculator and utility guides Find more guides that use real tool inputs and example numbers.
- All free tools Search every live tool, converter, calculator, AI helper, and browser utility.
Frequently asked questions
Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.
When should I use the Concrete Calculator?
Use it when your task matches one of these common needs: Estimate concrete for a simple slab, pad, walkway, or small project. Convert cubic feet to cubic yards before ordering ready-mix. It works best when you already know length, width, depth, and waste percent.
What is the Concrete Calculator doing with my inputs?
In plain language: The calculator uses cubic feet = length x width x (depth inches / 12), adjusted cubic feet = cubic feet x (1 + waste percent / 100), cubic yards = adjusted cubic feet / 27, cubic meters = adjusted cubic feet x 0.0283168, and bag counts = adjusted cubic feet / bag yield rounded up. The examples on the page are there so you can compare your inputs with a concrete slab example before copying the answer.
What do the main Concrete Calculator inputs mean?
Length and width: the inside form dimensions of the slab, pad, or walkway in feet. Depth: the average concrete thickness in inches, such as 4 for a common small slab. Extra waste: a cushion for uneven base, spillage, low spots, and ordering a little more than the exact volume.
How should I read the Concrete 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 is a planning estimate, not structural design or a supplier order guarantee. Forms, uneven ground, compaction, reinforcement, base prep, spillage, waste, truck minimums, weather, and exact bag yield can change what you need. Also check whether the depth is in inches, whether the slab shape is rectangular, whether the base is level, and whether you are ordering ready-mix cubic yards or buying bagged mix.
How do I calculate cubic yards for concrete?
Multiply length by width by depth in feet to get cubic feet, then divide by 27 for cubic yards. For a 10 ft by 12 ft slab at 4 inches thick, the exact volume is 40 cubic feet before waste and about 1.63 cubic yards with 10% waste.
Why does the calculator show 40 lb, 60 lb, and 80 lb bags?
Small jobs often use bagged concrete instead of a ready-mix truck. The bag counts use common approximate yields, then round up because you cannot buy part of a bag. Always check the yield printed on the exact bag before buying.
How much concrete is needed for a 10 by 12 slab at 4 inches?
With 10% waste, a 10 ft by 12 ft slab at 4 inches thick is about 44 cubic feet, 1.63 cubic yards, or 74 common 80 lb bags using a 0.6 cubic foot yield.
Should I order extra concrete?
Usually yes, but do it carefully. A small waste buffer helps with uneven base, form loss, spillage, and low spots. For ready-mix delivery, ask the supplier or contractor how much extra makes sense before ordering.
Does this handle footings, posts, stairs, or round forms?
This page is for a simple rectangular slab, pad, or walkway. Use a footing, post-hole, column, or steps calculator when the shape is different, and get professional help for structural or code-sensitive work.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.
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