Before starting any DIY poured concrete projectwhether setting a single fence post or laying a backyard patiothe first question is always: "How many bags of concrete do I need?" Buying too few stops your project in its tracks, while buying too many wastes money and breaks your back carrying heavy excess material.
The answer depends on three main variables: the volume of your project in cubic feet, the size of the bags you are purchasing (40lb, 60lb, 80lb, or 90lb), and the standard 10% waste contingency. In this guide, we break down exactly how many bags of concrete are required for standard project sizes.
Table of Contents
Bag Coverage Chart (40/60/80/90lb)
The volume each bag covers is based on standard high-strength mix yields. Knowing the cubic foot yield is the core component to solving the bags equation.
| Bag Size | Yield (Cubic Feet) | Yield (Cubic Yards) |
|---|---|---|
| 40 lb Bag | 0.30 ft | 0.011 yd |
| 60 lb Bag | 0.45 ft | 0.017 yd |
| 80 lb Bag | 0.60 ft | 0.022 yd |
| 90 lb Bag | 0.68 ft | 0.025 yd |
How Many Bags Per Cubic Yard
If a contractor tells you that you need "one yard" of concrete, you might be tempted to mix it yourself. However, it's crucial to understand how many bags of concrete per cubic yard you will actually need to mix by hand.
- 40lb bags: 90 bags per yard
- 60lb bags: 60 bags per yard
- 80lb bags: 45 bags per yard
Hand-mixing 45 bags of 80-pound concrete is extremely labor-intensive. This is why for any project over 1 cubic yard, ready-mix delivery is highly recommended.
How Many Bags for Common Projects
Here are quick estimations for standard home improvement projects using the most popular 80lb bag size:
| Project Type | Size / Dimensions | 80lb Bags Needed |
|---|---|---|
| Fence Post | 8" hole, 3ft deep | 2 bags |
| Sidewalk Section | 3x3 ft, 4 inches thick | 5 bags |
| AC Pad | 4x4 ft, 4 inches thick | 9 bags |
| Small Shed Base | 8x8 ft, 4 inches thick | 36 bags |
Quikrete vs Sakrete
When shopping at Home Depot or Lowe's, you will typically encounter Quikrete or Sakrete brands. Fortunately, the math remains the same regardless of the logo. A standard 80lb bag of Quikrete yields the exact same 0.60 cubic feet as an 80lb bag of Sakrete. The differences lie mainly in specific specialized blends (like fast-setting or high-strength 5000 PSI variants), not the base volume yields.
Use Our Free Calculators
To get a mathematically perfect answer tailored to your specific project dimensions and preferred bag sizes, use a dedicated bags of concrete calculator.
Universal Bag Calculator
Calculate totals for 40, 60, 80, and 90lb bags simultaneously.
Open Calculator80lb Bag Calculator
The specialized tool exclusively for industry-standard 80lb mix bags.
Open 80lb ToolFrequently Asked Questions
How many bags of concrete per cubic yard?
You need 45 bags of 80lb concrete, 60 bags of 60lb concrete, or 90 bags of 40lb concrete to equal one cubic yard.
Is it cheaper to buy bags or order a truck?
For projects under 0.5 cubic yards, mixing bags yourself is generally cheaper. For anything over 1 cubic yard, ordering ready-mix from a truck is more cost-effective and saves massive labor.
How many bags do I need for a 10x10 slab at 4 inches thick?
A 10x10 slab at 4 inches thick requires 1.23 cubic yards of concrete. This translates to exactly 56 bags of 80lb concrete.