Quantity & Materials Tool
Concrete Bag Calculator
Estimate 60lb and 80lb premix bags for slabs.
Slab Dimensions
# About This Calculator
Planning a DIY concrete project? Whether you're pouring a patio, a walkway, or setting fence posts, knowing exactly how much premix concrete to buy is crucial.
This calculator helps you estimate the number of 60lb or 80lb bags needed based on the dimensions of your slab. It ensures you don't run out mid-pour (a disaster!) or end up returning hundreds of pounds of heavy bags.
Thickness Guide
- 4 Inches: Standard for walkways, patios, and non-weight bearing slabs.
- 5-6 Inches: Recommended for driveways or areas parking heavy vehicles (RVs, trucks).
- 6+ Inches: Heavy-duty foundations or commercial use.
Pro Tips for Pouring
- Add 10% Extra: Spillage happens, and uneven ground can require more concrete than calculated. Always buy a few extra bags—you can return them, but you can't pause a pour to go to the store.
- Water Ratio: Don't add too much water! Soup-like concrete is weak. It should be the consistency of thick oatmeal.
How To Use
- Measure the **Length** and **Width** of the area you want to pour (in feet).
- Determine the **Thickness** of the slab (standard is 4 inches).
- Enter these values into the calculator.
- The tool will show you the exact volume in **Cubic Yards** and the number of 60lb or 80lb bags required.
Frequently Asked Questions
How many bags of concrete do I need for a 10x10 slab?+
For a 10x10 foot slab at 4 inches thick, you will need approximately 74 bags of 60lb concrete or 56 bags of 80lb concrete. This totals about 1.23 cubic yards.
Is it better to use 60lb or 80lb concrete bags?+
80lb bags are generally cheaper per pound, but they are much heavier to lift and mix. 60lb bags are easier to handle for DIY projects.
How thick should a concrete patio be?+
A standard concrete patio or walkway should be at least 4 inches thick. For driveways or areas supporting heavy vehicles, 5 to 6 inches is recommended.
How many 80lb bags make a yard?+
It takes approximately 45 bags of 80lb concrete to make one cubic yard. For 60lb bags, it takes about 60 bags.
Do I need to add gravel under my concrete slab?+
Yes, a 4-inch base of compacted gravel is highly recommended to provide drainage and prevent the slab from cracking due to soil movement.
Is Concrete Bag Calculator free to use?+
Yes, Concrete Bag Calculator on Matheric is completely free to use. We believe in accessible education and utility for everyone.