How much concrete does an 80 lb bag yield?

A standard 80 lb bag of premix concrete (such as Quikrete or Sakrete) yields approximately 0.60 cubic feet of finished concrete. A 60 lb bag yields about 0.45 cubic feet, and a 40 lb bag yields about 0.30 cubic feet. Yield varies slightly by mix type: high-strength mixes with less aggregate may yield marginally less volume per bag. To convert: 27 cubic feet equals 1 cubic yard, so you need roughly 45 bags of 80 lb mix per cubic yard of poured concrete.

Should I use bags or ready-mix?

Ready-mix is cost-effective above roughly 1 cubic yard (about 45 bags). Below that threshold, bagged mix is more practical because ready-mix trucks have a minimum delivery of 1 cubic yard and charge significant short-load fees. For a typical 4-inch driveway at 400 square feet you need about 5 cubic yards -- clearly ready-mix territory. For fence post footings, small walkway sections, or repair patches under 10 cubic feet, bags win on convenience and total cost.

What waste factor should I use?

Use a 5-10% waste factor for simple pours with clean formwork. Add 10% for slabs with irregular shapes or re-entrant corners where some material is difficult to place. Use 15% for vertical pours (walls, columns) where spillage and over-pour at the top are common. Uneven sub-grade can also add significant hidden volume -- every half inch of low spot across a 100 square foot slab adds 0.15 cubic feet of extra concrete. It is always better to order slightly more than needed; leftover concrete cannot be returned.

What mix ratios produce different concrete strengths?

Standard concrete uses a 1:2:3 ratio by volume (1 part cement : 2 parts sand : 3 parts coarse aggregate) with a water-to-cement ratio around 0.5, producing roughly 3,000 psi after 28 days. For 4,000 psi (driveways, structural slabs), use a 1:1.5:2.5 ratio and reduce water content. High-strength mixes above 5,000 psi require admixtures better handled by a ready-mix supplier. Adding water beyond the recommended ratio is the most common way to weaken concrete -- each 1-gallon addition per cubic yard reduces 28-day strength by approximately 200 psi.

How long does concrete need to cure before use?

Concrete reaches approximately 70% of its design strength in 7 days and 99% at 28 days under normal curing conditions (moisture retained, above 50 degrees F). Foot traffic is typically safe after 24-48 hours. Vehicle traffic should wait 7 days minimum, with full load-bearing use deferred to 28 days. Curing means keeping the concrete moist -- not just letting it sit. Cover with wet burlap or plastic sheeting, or apply a liquid curing compound to prevent moisture evaporation, which can reduce final strength by 50% if the surface dries too fast.

How do I calculate volume differently for slabs versus footings?

Slabs use length x width x depth in consistent units. A 10 ft x 10 ft slab at 4 inches (0.333 ft) deep = 33.3 cubic feet = 1.23 cubic yards. Footings are typically rectangular cross-sections running a linear distance: a 12-inch x 12-inch footing running 20 feet = 1 ft x 1 ft x 20 ft = 20 cubic feet = 0.74 cubic yards. Always measure footing depth to the bottom of the pour, accounting for the fact that footings must sit below the frost line -- which ranges from 12 inches in the deep South to 48 inches in northern states.

Concrete Yield Calculator

Calculate how many bags of concrete mix or cubic yards of ready-mix you need for slabs, walls, footings, and columns, with waste and cost included.

100% client-side. Inputs stay in your browser (ons-concrete-yield-inputs).

Bag yields follow common retail mix labels (0.30, 0.45, and 0.60 cu ft per bag). Your brand may differ; buy one extra bag on tight pours.

Bags needed

62 bags

Estimated cost

$341.00

Volume with waste

36.67 cu ft

Sections

Section nameShape

Length (ft)Width (ft)Depth (in)

Mix and pricing

Mix typeWaste factor (%)Price per bag ($)

Section	Shape	cu ft	cu yd
Main slab	Slab	33.33	1.23
Total (valid sections)		33.33	1.23
With 10% waste		36.67	1.36

Order quantity: 62 bags
Estimated cost: $341.00
Raw volume: 33.33 cu ft (1.23 yd)
Mix: 80 lb bags

How this tool works

Each section uses a shape-specific volume in cubic feet: slabs and footings use length times width times depth in feet; walls use length times height times thickness; round columns use pi times radius squared times height. We sum valid sections, apply your waste percent once on that total, then convert to bag count (always rounded up) or ready-mix yards (rounded up to the nearest tenth of a yard).

Worked example

A 10 by 10 foot patio slab at 4 inches thick is about 33 cubic feet, or 1.2 cubic yards before waste. With 10% waste you need roughly 37 cubic feet. That is about 62 eighty-pound bags, or about 1.4 yards from a ready-mix truck if you switch mix type in the tool.

Frequently asked questions

How much concrete does an 80 lb bag yield?
A standard 80 lb bag of premix concrete (such as Quikrete or Sakrete) yields approximately 0.60 cubic feet of finished concrete. A 60 lb bag yields about 0.45 cubic feet, and a 40 lb bag yields about 0.30 cubic feet. Yield varies slightly by mix type: high-strength mixes with less aggregate may yield marginally less volume per bag. To convert: 27 cubic feet equals 1 cubic yard, so you need roughly 45 bags of 80 lb mix per cubic yard of poured concrete.
Should I use bags or ready-mix?
Ready-mix is cost-effective above roughly 1 cubic yard (about 45 bags). Below that threshold, bagged mix is more practical because ready-mix trucks have a minimum delivery of 1 cubic yard and charge significant short-load fees. For a typical 4-inch driveway at 400 square feet you need about 5 cubic yards -- clearly ready-mix territory. For fence post footings, small walkway sections, or repair patches under 10 cubic feet, bags win on convenience and total cost.
What waste factor should I use?
Use a 5-10% waste factor for simple pours with clean formwork. Add 10% for slabs with irregular shapes or re-entrant corners where some material is difficult to place. Use 15% for vertical pours (walls, columns) where spillage and over-pour at the top are common. Uneven sub-grade can also add significant hidden volume -- every half inch of low spot across a 100 square foot slab adds 0.15 cubic feet of extra concrete. It is always better to order slightly more than needed; leftover concrete cannot be returned.
What mix ratios produce different concrete strengths?
Standard concrete uses a 1:2:3 ratio by volume (1 part cement : 2 parts sand : 3 parts coarse aggregate) with a water-to-cement ratio around 0.5, producing roughly 3,000 psi after 28 days. For 4,000 psi (driveways, structural slabs), use a 1:1.5:2.5 ratio and reduce water content. High-strength mixes above 5,000 psi require admixtures better handled by a ready-mix supplier. Adding water beyond the recommended ratio is the most common way to weaken concrete -- each 1-gallon addition per cubic yard reduces 28-day strength by approximately 200 psi.
How long does concrete need to cure before use?
Concrete reaches approximately 70% of its design strength in 7 days and 99% at 28 days under normal curing conditions (moisture retained, above 50 degrees F). Foot traffic is typically safe after 24-48 hours. Vehicle traffic should wait 7 days minimum, with full load-bearing use deferred to 28 days. Curing means keeping the concrete moist -- not just letting it sit. Cover with wet burlap or plastic sheeting, or apply a liquid curing compound to prevent moisture evaporation, which can reduce final strength by 50% if the surface dries too fast.
How do I calculate volume differently for slabs versus footings?
Slabs use length x width x depth in consistent units. A 10 ft x 10 ft slab at 4 inches (0.333 ft) deep = 33.3 cubic feet = 1.23 cubic yards. Footings are typically rectangular cross-sections running a linear distance: a 12-inch x 12-inch footing running 20 feet = 1 ft x 1 ft x 20 ft = 20 cubic feet = 0.74 cubic yards. Always measure footing depth to the bottom of the pour, accounting for the fact that footings must sit below the frost line -- which ranges from 12 inches in the deep South to 48 inches in northern states.

Related tools

House flipping simulator for rehab budget and profit on a flip.
Cap rate calculator for rental NOI and property value.
Freight class calculator for LTL density and NMFC class quotes.
Wholesale markup calculator for distributor pricing on materials.