How many 80 lb bags of concrete does a 10 × 10 slab take?

A 10 × 10 ft concrete slab 4 inches thick takes 56 bags of 80 lb (33.33 ft³ ÷ 0.6 ft³ per bag), before the 4–10% ordering allowance.

How much concrete does a round post hole take?

A round post hole 12 inches wide and 3 feet deep takes 2.36 ft³ of concrete, or 4 bags of 80 lb. Add a round hole or tube in the calculator and enter the diameter, depth and count.

Can concrete be poured thinner than 2 inches?

No, Quikrete lists 2 inches as the minimum placement thickness for its Concrete Mix. Slabs and walks need 4 inches.

Concrete Calculator

Fresh concrete weighs 3,780–4,050 lb per cubic yard. Enter a slab's length, width and thickness, or a round hole's diameter and depth, below to get cubic yards, bags and cost.

Shape

Area

Length ft

Width ft

Count

Depth in

Tape readings work: 10' 6", 10½. Sloped? Type the depth as 2-6. Other material? Use the cubic yard calculator.

Order

1.75 cubic yards to order

rounded up to the nearest ¼ yd³

Solid: exact 1.48 yd³. Dashed: what you order, 1.75 yd³ (+5% waste, rounded up). Person: 6 ft, for scale.

Weight: 3.31–3.54 tons (fresh, normal-weight)
Bags: Order bulk — bags would be 70 × 80 lb
Cost: $208–$284

NRMCA advises ordering 4–10% over plan volume for uneven subgrade and waste. Under 3–10 yd³ (varies by supplier) ready-mix usually carries a short-load fee — ask for it with the quote, or compare bags.

Details: exact volume, bags vs bulk, order sheet

Exact 1.48 + 5% = 1.56 yd³ · 40 ft³ · 1.13 m³

At 4 in deep, 1 yd³ covers 81 ft².

You need 1.75 cubic yards of concrete ≈ 3.31–3.54 tons (fresh, normal-weight).

Bags vs bulk: price per 80 lb bag, $

Order sheet for your supplier

Concrete weight: fresh, normal-weight (NRMCA, ACI). Cost: reference range, ready-mix, before delivery and short-load fees (HomeGuide Jan 2026; supplier price lists 2026); local prices vary.

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Concrete slab thickness

Concrete slab thickness is 4 inches for slabs, sidewalks and walkways, per Sakrete's flatwork directions.

A slab-on-ground floor needs at least 3½ inches under the residential code (IRC R506.1). A public sidewalk in New York is 4 inches thick and 6 inches where it crosses a driveway (NYSDOT).

The table shows one 10 × 10 ft concrete slab at each of these thicknesses.

Thickness	Cubic feet	Cubic yards	80 lb bags
3½ in	29.17	1.08	49
4 in	33.33	1.23	56
6 in	50	1.85	84

A 6-inch concrete slab takes 1.5 times the concrete of a 4-inch slab of the same size.

Concrete bags vs ready-mix

Concrete bags yield 0.3 cu ft per 40 lb bag up to 0.6 cu ft per 80 lb bag, so one cubic yard takes 90 to 45 bags.

Bag	Yield (ft³)	Bags per yd³
40 lb	0.3	90
50 lb	0.375	72
60 lb	0.45	60
80 lb	0.6	45

Yields come from the Quikrete and Sakrete data sheets; bag counts are 27 ÷ yield, rounded up, with no waste. Sakrete 5000 Plus Concrete Mix 60 lb yields 0.47 cu ft, or 58 bags per yard.

A ready-mix truck carries 9–11 cubic yards (NRMCA). Loads below a supplier's minimum carry a short-load fee, and the fee varies by supplier.

Concrete weight, bag sizes and ready-mix price per cubic yard
Material	lb per yd³	tons per yd³	Bags	$ per yd³
Concrete	3,780–4,050	1.89–2.03	80 lb, 60 lb, 50 lb, 40 lb	$119–$162

Weight basis: concrete fresh, normal-weight. Prices are reference ranges from dated cost guides and supplier lists (updated September 2026); local prices vary. Sources: NRMCA; ACI; Quikrete; Sakrete; HomeGuide; GSI Concrete (PA); Townsend Concrete (CA).

Concrete cost per yard

Ready-mix concrete costs $119–$162 per cubic yard before delivery, short-load and weekend fees (HomeGuide Jan 2026; supplier price lists 2026). Stronger mixes cost more.

Mix strength	$ per yd³
2,000 PSI	$119
4,000 PSI	$129
5,000 PSI	$147

Short-load fees apply below a supplier threshold, seen from 3 to 10 yd³ in our sources. Examples: +$53 per yd³ for loads under 10 yd³ (HomeGuide); $15–$17 per yd³ short-load delivery (Fixr). Delivery: $55–$65 per full truck (Fixr). Ask for both with the quote.

PSI prices: HomeGuide, Jan 2026, delivered within 20 miles. Reference ranges, not quotes.

Concrete ordering allowance

Concrete orders need 4–10% over plan volume for uneven subgrade and waste, per NRMCA.

An ⅛-inch thickness error on a 4-inch concrete slab leaves the pour about 3% short. Ready-mix is sold by fresh volume, and hardened concrete in place can occupy about 2% less volume.

A yard of fresh concrete weighs 3,780–4,050 lb (1.89–2.03 tons), so a full 9–11 yd³ mixer carries 17–22.3 tons (NRMCA). No separate cured weight is published.

Concrete calculator FAQ

How many 80 lb bags of concrete does a 10 × 10 slab take?: A 10 × 10 ft concrete slab 4 inches thick takes 56 bags of 80 lb (33.33 ft³ ÷ 0.6 ft³ per bag), before the 4–10% ordering allowance.
How much concrete does a round post hole take?: A round post hole 12 inches wide and 3 feet deep takes 2.36 ft³ of concrete, or 4 bags of 80 lb. Add a round hole or tube in the calculator and enter the diameter, depth and count.
How much does a yard of concrete cost?: A yard of ready-mix concrete costs $119–$162 before delivery and short-load fees (HomeGuide Jan 2026; supplier price lists 2026). In 80 lb bags, a yard is 45 bags; multiply by your store's bag price.
Can concrete be poured thinner than 2 inches?: No, Quikrete lists 2 inches as the minimum placement thickness for its Concrete Mix. Slabs and walks need 4 inches.