Readymix Concrete Calculator
Whether you’re pouring a small patio or a large foundation, calculating the right amount of concrete is essential to avoid waste or delays. Our Ready-Mix Concrete Calculator is a fast and accurate tool that helps DIYers, contractors, and builders determine the volume of concrete required for any project. With just a few inputs—length, width, and thickness—this calculator provides you with results in cubic feet, cubic yards, and the number of 80 lb bags needed.
Why Use a Concrete Calculator?
Concrete is usually ordered by volume, measured in cubic yards. Estimating too little can result in costly delays, while ordering too much leads to waste and added expense. Our calculator ensures you get the most accurate volume needed, helping you:
- Minimize waste and cost
- Save time with fast estimations
- Order the right quantity from suppliers
- Plan logistics, storage, and labor
How to Use the Ready-Mix Concrete Calculator
Follow these simple steps to get your concrete estimate in seconds:
Step-by-Step Instructions:
- Enter Length (ft):
Type in the length of your slab, pad, or area in feet. For example, a driveway might be 20 ft long. - Enter Width (ft):
Input the width in feet. A standard single-car driveway is typically around 10 ft wide. - Enter Thickness (in):
Specify the thickness in inches. Most slabs are between 4–6 inches thick. - Click “Calculate”:
Press the “Calculate” button. The tool instantly displays:- Volume in Cubic Feet
- Volume in Cubic Yards
- Number of 80 lb Bags Required
- Optional – Reset Inputs:
Use the “Reset” button to clear all fields and start over with a new measurement.
Practical Examples
Example 1: Small Patio
- Length: 10 ft
- Width: 8 ft
- Thickness: 4 in
Results:
- Cubic Feet: 26.67 ft³
- Cubic Yards: 0.99 yd³
- 80 lb Bags Needed: 45
Example 2: Garage Slab
- Length: 20 ft
- Width: 20 ft
- Thickness: 6 in
Results:
- Cubic Feet: 200 ft³
- Cubic Yards: 7.41 yd³
- 80 lb Bags Needed: 334
These examples demonstrate how quickly the tool provides the necessary information to place an accurate order with your concrete supplier.
Helpful Information & Use Cases
Common Concrete Thickness Recommendations:
- Driveways: 4–6 inches
- Garage Floors: 6 inches
- Sidewalks & Walkways: 4 inches
- Patios: 4 inches
- Foundations & Slabs: Varies based on structural needs
Why Use 80 lb Bags as a Metric?
Most ready-mix concrete is sold in 80 lb bags at hardware stores. One bag covers approximately 0.6 cubic feet. This allows DIYers to plan how many bags they’ll need for small to medium-sized projects.
When to Order in Yards Instead of Bags
If your project exceeds 1 cubic yard (27 cubic feet), it’s usually more cost-effective to order ready-mix concrete by the yard from a local supplier, especially for large slabs or foundations.
Frequently Asked Questions (FAQs)
1. How accurate is the concrete calculator?
It provides highly accurate estimates based on your input dimensions. Always add 5–10% extra for spillage or variation.
2. How do I convert inches to feet for thickness?
The calculator does this automatically. Just input thickness in inches; it converts to feet internally.
3. How many cubic feet are in a cubic yard?
There are 27 cubic feet in one cubic yard.
4. How much concrete does an 80 lb bag yield?
An 80 lb bag yields approximately 0.6 cubic feet of concrete.
5. Can I use this calculator for columns or footings?
Yes, but you’ll need to calculate volume using cylinder or trapezoidal formulas if the shape isn’t rectangular.
6. What’s the best thickness for a concrete driveway?
Most residential driveways should be at least 4 inches, but 6 inches is recommended for heavier vehicles.
7. Is this calculator suitable for metric units?
Currently, this tool uses feet and inches. You’ll need to convert metric units to imperial before entering values.
8. What if I’m using 60 lb or 40 lb bags instead?
An 80 lb bag = 0.6 ft³
- 60 lb bag ≈ 0.45 ft³
- 40 lb bag ≈ 0.3 ft³
You can adjust the total bags accordingly based on these conversions.
9. Does this include waste or overage?
No. It’s best to order an additional 5–10% to cover spillage, over-excavation, and errors.
10. Is concrete heavier when wet or dry?
Wet concrete is heavier due to water content, but for volume calculations, that doesn’t affect the estimate.
11. Can I save or print my results?
While this version doesn’t include a save feature, you can screenshot or print your browser page for records.
12. Can I use this calculator on mobile devices?
Yes, the calculator is fully responsive and mobile-friendly.
13. Does this calculator work for sloped surfaces?
No. For sloped or irregular shapes, calculate average thickness and enter that value.
14. How do I know how much concrete to buy for a round patio?
Use the formula for the area of a circle: π × radius². Multiply by thickness (in feet) for cubic footage.
15. Is this calculator free to use?
Yes, it’s completely free with no login required.
16. Where can I buy concrete bags?
Most hardware stores like Home Depot, Lowe’s, and local building supply centers carry 80 lb bags.
17. What’s the minimum amount of concrete I can order from a supplier?
Many suppliers require a minimum of 1 yard or more. Always check with local providers.
18. Can I mix concrete myself for large projects?
It’s not recommended for large pours (over 1 yard). Use ready-mix delivery for efficiency and consistency.
19. What PSI should my concrete mix be?
- Sidewalks & patios: 3,000–3,500 PSI
- Driveways: 4,000+ PSI
- Foundations: 4,000–5,000 PSI
20. Do I need rebar or reinforcement with my concrete?
For most structural applications (driveways, foundations), reinforcement is recommended to prevent cracking.
Final Thoughts
Our Ready-Mix Concrete Calculator helps eliminate guesswork so you can confidently plan and execute your construction projects. Whether you’re tackling a DIY sidewalk, preparing a foundation slab, or estimating a full driveway pour, this tool saves you time, money, and unnecessary effort.