Concrete calculator

Pick a slab or round footings, enter the dimensions, and compare bagged mix with a ready-mix truck. Bag yields default to what most 60 and 80 lb bags list; check yours.

Materials takeoff

Concrete Calculator · https://estimahome.com/concrete-calculator/

Pour: Slab (rectangle)Slab length: 10 ftSlab width: 10 ftSlab thickness: 4 in

Volume: 33.33 cu ft · 1.23 cu yd
With extra: 36.67 cu ft · 1.36 cu yd
80 lb bags: 62
60 lb bags: 82

Option A: 80 lb bags
No.	Item	Qty	Unit	Unit cost	Amount
1	Concrete mix, 80 lb	62	bag	$6.50	$403.00

Subtotal: $403.00
Likely range: $342.55 – $463.45

Option B: 60 lb bags
No.	Item	Qty	Unit	Unit cost	Amount
2	Concrete mix, 60 lb	82	bag	$5.25	$430.50

Subtotal: $430.50
Likely range: $365.93 – $495.08

Option C: ready-mix truck
No.	Item	Qty	Unit	Unit cost	Amount
3	Ready-mix concrete	1.5	cu yd	$175.00	$262.50

Subtotal: $262.50
Likely range: $223.13 – $301.88

Ready-mix plants often add delivery and short-load charges for small orders.
Not included: gravel base, rebar or mesh, form boards.

Buy these materials

Pick one bag size. Ready-mix is ordered from a local plant.

62 80 lb bags of concreteAmazon search for 80 lb bags of concrete (opens in new tab)
82 60 lb bags of concreteAmazon search for 60 lb bags of concrete (opens in new tab)

Links open a store search for each item. Check sizes and grades against your plan.

Quick reference

One cubic yard is 27 cubic feet.
A 10 × 10 ft slab 4 in thick is 33.33 cu ft (1.23 cu yd) of concrete.
At 0.6 cu ft per 80 lb bag, a cubic yard takes 45 bags; at 0.45 cu ft per 60 lb bag, 60 bags.

How it's calculated

⌈x⌉ means round up to the next whole unit; ⌊x⌋ means round down. Every quantity you buy is rounded up.

Slab (cu ft) = length × width × thickness ÷ 12
Footings (cu ft) = count × π × (diameter ÷ 24)² × (depth ÷ 12)
Cubic yards = cubic feet ÷ 27
Order volume = volume × (1 + extra ÷ 100)
80 lb bags = ⌈ order volume ÷ 80 lb yield ⌉
60 lb bags = ⌈ order volume ÷ 60 lb yield ⌉
Ready-mix order = order yards rounded up to the next ¼ yd
Cost per option = quantity × unit price; range = cost × (1 ± range % ÷ 100)

Worked example

A 10 × 10 ft slab 4 in thick is 10 × 10 × 4 ÷ 12 = 33.33 cu ft, or 1.23 cu yd. With 10% extra that becomes 36.67 cu ft. At 0.6 cu ft per bag that is 62 bags of 80 lb mix ($403.00), or 82 bags of 60 lb mix at 0.45 cu ft each ($430.50). A ready-mix order would be 1.5 cu yd ($262.50 before delivery charges).

Questions

How many bags of concrete are in a yard?

About 45 bags of 80 lb mix or 60 bags of 60 lb mix, based on yields of 0.60 and 0.45 cu ft per bag.

When does ready-mix make more sense than bags?

Past about one cubic yard, mixing bags by hand gets slow and hard to finish before it sets. Call a local plant for pricing; many charge extra for orders under a few yards.

How thick should a concrete slab be?

4 in is standard for patios, walks and shed floors. Driveways and slabs that carry vehicles are usually 5 to 6 in with reinforcement. Local code and soil conditions decide.

How much extra concrete should I order?

5 to 10% covers spillage, an uneven base and forms that bow. Running short mid-pour is worse than a few leftover bags.

Cite: “Concrete Calculator.” EstimaHome, https://estimahome.com/concrete-calculator/. Updated 2026-10-20. Formulas in machine-readable form: /api/calculators.json.