Concrete Bag Calculator — ft, bags, cost comparison
How to use this calculator
Pick a preset for the most common small pours, or enter your own volume. The calculator rounds every bag size up and flags the cheapest option per bag size once prices are entered — the number you see is what to load in the truck, not a theoretical minimum.
Direct volume — enter yd³ or ft³ if you already know the volume.
Dimensions — enter L × W × D in feet and inches.
Waste — 10% for clean formwork, 15% for footings poured against soil.
| Bag Size | Yield | Bags | Weight | Cost |
|---|---|---|---|---|
| 40 lb | ft³ | — | — | — |
| 50 lb | ft³ | — | — | — |
| 60 lb | ft³ | — | — | — |
| 80 lb | ft³ | — | — | — |
| 90 lb | ft³ | — | — | — |
Saved Calculations
| Time | Volume | 40 lb | 60 lb | 80 lb | Best Cost |
|---|
How Many Bags of Concrete Do I Need?
Bagged concrete (Quikrete, Sakrete, Sika) is economical only for small pours — footings, post bases, slab repairs, and pads up to roughly 1 yd³. Above that, ready-mix delivery is almost always cheaper per yard once you account for mixing labor. This tool compares the 40, 50, 60, 80, and 90 lb sizes so you can see the break-even at a glance.
How to use it
Enter a known volume in yd³ or ft³, or switch to Dimensions and type length × width × depth (feet, inches, and fractions). A 10 ft × 10 ft slab at 4 in is the default. The waste slider adds an allowance for spillage, sub-base irregularity, and partial bags — 10% is typical for flatwork, 15% for footings poured against rough soil.
Bag yield reference
ASTM C387/C387M covers packaged concrete materials and yield testing, but bag weight alone does not establish one universal yield. The calculator starts with representative current US product values; always replace the yield with the value printed on the selected bag. The displayed concrete weight uses 150 lb/ft³ only as an estimating assumption for normal-weight concrete.
Formulas
Volume: Vft³ = Lft × Wft × (Din ÷ 12); divide by 27 for yd³.
Bags: N = ⌈Vft³ × (1 + waste) ÷ yieldbag⌉ (rounded up — you cannot buy a partial bag).
Cost: per size = N × price/bag; the lowest non-zero total is flagged as best value.
Related concrete calculators
For structural pours, size the section first: the concrete beam calculator and concrete column calculator return both volume and rebar. For larger flatwork use the concrete volume calculator, and for vertical work the concrete wall calculator. Site work is covered by the curb & gutter calculator and the concrete stairs calculator.
FAQ
Which bag size is best? 80 lb bags are the most popular for medium projects — best balance of yield and handling weight. Use 40–60 lb bags for small repairs or back-friendly handling, and 90 lb bags for large volumes.
How many 80 lb bags per yard? Approximately 45 bags of 80 lb concrete per cubic yard (27 ft³ ÷ 0.6 ft³ per bag = 45). At ~45 bags/yd³, ready-mix usually wins above 1–2 yd³.
Why round up every bag size? Bags are sold whole, and a short pour cannot be patched cleanly once it sets, so the calculator always ceilings the bag count after applying waste.
Ordering tips
In 2025 USA, 80 lb bags run about $5.50–7.50 (Quikrete/Sakrete standard), 60 lb $4.50–6, and high-early Type III fast-setting bags $7–10. The most common estimator mistake is buying for the dry volume printed on the bag and skipping the waste line — partial bags, spillage, and a slightly over-dug post hole easily add 10–15%. Above roughly 1 yd³ (about 45 of the 80 lb bags), price out ready-mix instead: even with a short-load fee a truck usually wins on $/yd³ and saves a full day of mixing. Concrete strength, air entrainment, exposure class and permitted use must follow the project documents, the locally adopted code and the product data sheet; bag strength alone does not establish suitability for every footing, slab or freeze-thaw exposure.
Calculation notesWhat this calculator doesOpen the formula basis, references and assumptions when you need to verify the detailed method.Review details
Required concrete volume is divided by the selected bag yield and rounded up to purchasable whole bags, with editable waste and price inputs.
Reference context
- • ACI 318
- • ASTM C387
- • supplier yield and density data
Important assumptions
- • Dimensions, quantities and prices entered by the user are correct.
- • Waste, laps, overlaps, compaction and delivery allowances must match the actual project.
- • Results are preliminary takeoff estimates, not a sealed structural design or permit approval.
Quality notes updated: August 1, 2026. The repository includes per-page checks for browser errors, populated results, metadata, US-market visibility, duplicate IDs and shared quality controls.
Reference names describe the applicable design and product context; they do not replace a project-specific code review. Local codes, drawings, specifications and manufacturer instructions govern the final work. Report a calculation or interface issue.
