Concrete / Bag quantity estimator
Concrete Bag Calculator
Plan whole bags of premixed concrete. Enter dimensions or a known volume, then set your product's yield.
Your material estimate
Live resultConcrete needed · Bags to buy
62bags
10% extra included. Rounded up once to whole bags.
Order volume36.67 ft³1.36 yd³
- Base volume
- 33.33 ft³
- + 10% extra
- 3.33 ft³
- Raw bags
- 61.11
- Bags to buy
- 62 bags
- Selected bag
- 80 lb
- Yield used
- 0.60 ft³ per bagPreset reference
Confirm the yield on your chosen product before purchasing.
Common Bag Size Comparison
Comparison uses standard reference yields.
| Bag | Reference yield | Bags to buy |
|---|---|---|
| 40 lb | 0.30 ft³ | 123 |
| 50 lb | 0.375 ft³ | 98 |
| 60 lb | 0.45 ft³ | 82 |
| 80 lb | 0.60 ft³ | 62 |
Understand your estimate
How the Concrete Bag Calculator Works
The calculator first determines the amount of concrete required from either your project dimensions or a concrete volume you already know. It then adds the selected extra-material allowance and divides the resulting volume by the yield of one bag of concrete.
The formula
- Base volume = length × width × thickness
- Or base volume = known concrete volume
- Order volume = base volume × (1 + extra % / 100)
- Raw bags = order volume / yield per bag
- Estimated cost = whole bags to buy × price per bag
Extra is applied before a single final round up. Calculations use canonical cubic meters and decimal arithmetic; rounded display values are never used to calculate bags.
Bag yield
Bag yield varies by product and manufacturer. The calculator provides reference yields for common bag sizes, but you can edit the yield to match the concrete mix you plan to buy.
40 lb → 0.30 ft³; 50 lb → 0.375 ft³; 60 lb → 0.45 ft³; 80 lb → 0.60 ft³. Weight describes the bag and selects a reference; the current yield input determines the primary estimate.
Extra concrete
A 10% extra allowance is included by default to help account for uneven subgrade, spillage, waste, and small differences between estimated and actual yield.
Select 0%, 5%, 10%, or a custom allowance from 0% to 100%.
Understanding the comparison
The common bag-size comparison uses reference yields for standard 40 lb, 50 lb, 60 lb, and 80 lb bags. If you enter a custom yield, your custom value is used for the primary estimate while the comparison continues to show reference values.
Assumptions & limitations
Dimensions mode covers a rectangular pour only, such as a slab, pad, or sidewalk section. Known Volume mode accepts a volume already calculated for your project; it does not assess the project design. Input modes retain their own values.
Yield is approximate and editable. Cost is optional, in USD, and excludes tax, delivery, and labor. No water ratio, mix design, PSI, reinforcement, strength, engineering, or ready-mix recommendation is made.
Frequently asked questions
How many bags of concrete do I need?
Find your volume from dimensions or Known Volume mode, add the selected extra allowance, divide by your product's yield per bag, and round up once to whole bags.
How many bags of concrete are in a cubic yard?
It depends on bag yield: divide 27 ft³ by the yield per bag, then round up. At the reference 0.60 ft³ yield, one cubic yard requires 45 bags before extra. Use your product's yield and the calculator for your chosen allowance.
How much concrete does an 80 lb bag make?
The reference yield is approximately 0.60 ft³. Check the manufacturer's published yield for the mix you plan to buy and edit the input accordingly.
How much does a 60 lb bag make?
The reference yield is approximately 0.45 ft³. Actual product yield may differ; check the bag or manufacturer specifications.
How much extra concrete should I allow?
The default is 10%, and you can change it from 0% to 100%. Confirm an appropriate allowance for uneven subgrade, spillage and waste with your supplier or project specification.
Why can bag yield vary?
Product formulation, manufacturer specifications, mixing, and placement conditions can affect yield. Use the published yield for the actual product and appropriate jobsite allowance.
Can I enter concrete volume directly?
Yes. Select Known Volume and enter ft³, yd³, m³ or liters. The same extra, yield and whole-bag calculation is used.
Does this calculator tell me what concrete strength I need?
No. It estimates material quantity only and does not select strength or provide structural or code-compliance advice.