Cement Calculator
Bags of portland cement or premixed concrete for any pour
What is cement calculator?
A cement calculator sizes the bags you need for a concrete pour. The first job of this tool is terminology cleanup: most people who search “cement calculator” actually mean “concrete calculator” — they want to know how many bags of premixed product to buy.
Cement vs concrete — the precise definitions. Cement is one ingredient — portland cement is a finely ground powder that hydrates with water to form a binder. Concrete is the finished structural material: cement + sand + gravel + water + admixtures. You’d never pour pure cement (it’s brittle and shrinks badly); you’d pour concrete. The product on the hardware store shelf labeled “concrete mix” is what 95% of DIY pourers actually need.
This calculator’s default is premixed concrete bags — Quikrete, Sakrete, or store brand. The math uses the published yield of 0.60 ft³ per 80-lb bag of standard concrete mix. For 60-lb bags, 0.45 ft³; for 40-lb bags, 0.30 ft³.
If you actually need raw portland cement. The standard mix ratio is 1:2:3 by volume — 1 part portland cement, 2 parts sand, 3 parts gravel. For 1 cubic yard of concrete (27 ft³), that’s roughly 4.5 ft³ of portland cement (~5.5 of 94-lb bags), 9 ft³ of sand, and 13.5 ft³ of gravel. The total volume of finished concrete is less than the sum because the cement and water fill voids between the aggregates.
When raw cement is the right call. For pours over ~5 cubic yards where you can source sand and gravel cheaply, mixing from raw ingredients saves money. For most DIY work, premixed bags are dramatically simpler — same yield, no measuring, predictable strength.
Specialty cements. Type II portland resists sulfate attack — use in soil with high sulfate content. Type III is high-early-strength — sets faster, used in cold-weather pours. White portland cement is for decorative work where gray staining matters. None of these change the bag math; the yield is consistent across portland cement types.
When to use a cement calculator
- Buying premixed concrete — If you're buying a bag labeled 'concrete mix' (Quikrete, Sakrete, store brand), this calculator sizes the bag count using the standard 0.60 ft³/80-lb yield.
- Buying portland cement separately — If you're buying portland cement (the binder powder) and adding sand and gravel yourself, you need different math — see the FAQ for the 1:2:3 ratio.
- Clarifying terminology — Many homeowners use 'cement' to mean 'concrete.' This calculator outputs the bag count for premixed concrete by default — the most common case for DIY pourers.
How to use the Cement Calculator
- Confirm what you're actually buying — If your bag says 'concrete mix' or 'high-strength concrete,' you need premixed bags — this calculator. If it says 'portland cement,' it's just the binder; you need separate sand and gravel.
- Pick a shape — Slab/Pad for flat pours, Footing for rectangular, Column for sonotubes. The calculator handles unit conversion.
- Read the bag count — The output is for premixed concrete bags (0.60 ft³/80-lb yield). For raw portland cement, see the FAQ for the 1:2:3 mix ratio math.
- Add 1-2 spare bags — 10% waste is built in. For uneven subgrade or footings with rebar, bump waste to 15% in the input.
Worked examples
Patio: 10 × 12 ft × 4 in (premixed)
Input: Slab tab: 10 ft × 12 ft × 4 in
Output: 1.48 cu yd / 67 of 80-lb bags premixed concreteFooting: 4 × 4 × 1 ft (premixed)
Input: Footing tab: 4 ft × 48 in × 12 in
Output: 0.59 cu yd / 27 of 80-lb bags premixed concreteSonotube: 12 in × 6 ft (premixed)
Input: Column tab: 12 in dia × 6 ft
Output: 0.17 cu yd / 8 of 80-lb bags premixed concrete