Yard & BuildMaterial Calculators List 0

Aisle 1, Concrete & masonry

Concrete Calculator

A 10 × 10 ft slab 4 inches thick takes 1.23 cubic yards of concrete, or 56 bags of 80 lb mix, before extra for waste. Pick a shape, enter your sizes in any unit, and get cubic yards and bag counts for every bag size.

What are you pouring?
Extra for waste, and price
The ready-mix industry advises 4–10% extra for uneven subgrade, spillage and form spread.
Concrete orderStandard mix
1.36cu yd
36.7 cu ft · 1.04 m³ to order
Weight2.57–2.75 tons
Finished volume1.23 cu yd
Bagged mix
80 lb bags (0.60 cu ft)62 bags
60 lb bags (0.45 cu ft)82 bags
50 lb bags (0.375 cu ft)98 bags
40 lb bags (0.30 cu ft)123 bags

Bag counts use the yields printed on QUIKRETE and SAKRETE bags. Ready-mix trucks carry 8–12 cu yd; ask your supplier about small loads.

10 ft10 ftthick 4 in
Plan view of your slab (not to scale when very long or narrow).

How this was calculated

  1. Slab: length 10 ft, width 10 ft, thickness 4 in → 33.33 cu ft
  2. 33.33 cu ft ÷ 27 = 1.235 cu yd
  3. Extra for waste + 10% → 36.67 cu ft = 1.358 cu yd
  4. Weight = 1.358 cu yd × 1.89–2.03 tons/cu yd = 2.57–2.75 tons
  5. 80 lb bags (0.60 cu ft): 36.67 ÷ 0.6 cu ft = 61.11 → round up to 62
  6. 60 lb bags (0.45 cu ft): 36.67 ÷ 0.45 cu ft = 81.48 → round up to 82
  7. 50 lb bags (0.375 cu ft): 36.67 ÷ 0.375 cu ft = 97.78 → round up to 98
  8. 40 lb bags (0.30 cu ft): 36.67 ÷ 0.3 cu ft = 122.22 → round up to 123

How to calculate concrete

Concrete is ordered by the cubic yard, and bagged mix is sold by weight with a stated yield in cubic feet. Find the volume in cubic feet, then convert.

cubic feet = length (ft) × width (ft) × thickness (in) ÷ 12
cubic yards = cubic feet ÷ 27
bags = cubic feet ÷ yield per bag, rounded up

For a round post hole or form tube the volume is π × (diameter ÷ 2)² × depth, with every size in feet.

Why order extra? Forms bow, and ground that is only ⅛ inch low under a 4 inch slab already takes about 3% more concrete than the plan shows.[1]

Example: a 10 × 10 ft patio slab, 4 inches thick

  1. Volume: 10 × 10 × 4 ÷ 12 = 33.33 cu ft
  2. Cubic yards: 33.33 ÷ 27 = 1.23 cu yd
  3. With 10% extra: 36.67 cu ft = 1.36 cu yd
  4. 80 lb bags: 36.67 ÷ 0.60 = 61.1 → 62 bags (or 82 bags of 60 lb)

Example: six 12-inch form tubes, 4 ft deep

  1. One tube: π × (1 ÷ 2)² × 4 = 3.14 cu ft (Sonoco lists 0.80 cu ft per foot for a 12 in tube[2])
  2. Six tubes: 18.85 cu ft = 0.70 cu yd
  3. 60 lb bags: 18.85 ÷ 0.45 = 41.9 → 42 bags before extra

Choose Column / hole above, set Diameter to 12 in, Depth or height to 4 ft, How many to 6 and Extra for waste to 0 to get the same answer; with the default 10% extra it shows 47 bags.

Bags per cubic yard

At 40, 60 and 80 lb, QUIKRETE and SAKRETE list the same yields for standard concrete mix, which works out to 0.0075 cubic feet per pound.[3][4] Lightweight mixes yield much more per bag, so use the number on your bag if it differs.

BagYieldBags per cu ydCovers at 4 in thick
80 lb bags0.6 cu ft451.80 sq ft
60 lb bags0.45 cu ft601.35 sq ft
50 lb bags0.375 cu ft721.13 sq ft
40 lb bags0.3 cu ft900.90 sq ft

A cubic yard of 80 lb bags is 45 bags and 3,600 lb of dry mix to carry and mix by hand.[5]

Bags or a ready-mix truck?

Ready-mix trucks carry 8 to 12 cubic yards, and the National Ready Mixed Concrete Association advises ordering 4–10% more than the calculated volume.[6] Suppliers set their own minimums and fees for small loads; one Indiana producer, for example, delivers from 1 cubic yard in quarter-yard steps and adds a fee under 4.25 yards.[7] Call your local plant before you decide.

For comparison, the 10 × 10 ft slab above is 1.36 cubic yards with extra, which is 62 bags and about 4,960 lb of dry mix.

How thick should a concrete slab be?

UseThicknessSource
Patio4 inQUIKRETE[8]
Sidewalk or walkat least 4 inQUIKRETE[9]
Driveway, cars4 inQUIKRETE[10]
Driveway, trucks or heavy vehicles5–6 inQUIKRETE[10]
Floor slab on ground (e.g. garage)3½ in minimum by codeIRC R506.1[11]

Local codes and your soil can require more. The Ohio Ready Mixed Concrete Association says 3½–4 inches is generally enough for residential driveways, patios and walks, unless heavy trucks will park on them regularly.[12]

How much concrete weighs

Normal-weight concrete weighs 140–150 lb per cubic foot, typically about 145.[13][14] A cubic yard is therefore about 3,780–4,050 lb, or roughly 2 tons.

Water per bag

For an 80 lb bag of QUIKRETE Concrete Mix, start with about 3 quarts of water and add more only as needed, up to about 4.5 quarts.[3] Extra water makes the mix easier to place but weaker.

Post holes

QUIKRETE’s rule of thumb is a hole three times the width of the post, one third of the post’s length deep, with 6 inches of gravel in the bottom for drainage.[15] Subtract the post from the hole volume when you estimate: for a 4×4 post (3½ in actual), a 10½ in hole with 30 in of concrete above the gravel needs about 1.29 cu ft.

Structural work. Footings, piers and posts that carry a deck, roof or wall must meet your local building code, including frost depth. This calculator gives quantities only; check with your building department. Call 811 before you dig so buried utility lines are marked.

Control joints

Cut or tool joints to control cracking. The NRMCA guideline is a spacing of 24 to 36 times the slab thickness, so about 8–12 ft for a 4 in slab (and no more than 15 ft), with a depth of at least a quarter of the thickness.[16]

Questions people ask

How many 80 lb bags of concrete do I need for a 10x10 slab?

At 4 inches thick, a 10 × 10 ft slab is 33.33 cubic feet. Divided by 0.60 cubic feet per bag that is 56 bags, or 62 with 10% extra.

How many 60 lb bags of concrete does a 10 × 10 slab take?

At 4 inches thick, 75 bags of 60 lb mix (0.45 cubic feet each), or 82 with 10% extra.

How many bags of concrete are in a yard?

A cubic yard (27 cubic feet) takes 45 bags of 80 lb, 60 bags of 60 lb, 72 bags of 50 lb or 90 bags of 40 lb standard mix.

How much does a 50 lb bag of concrete cover?

A 50 lb bag yields 0.375 cubic feet, which covers about 1.13 sq ft at 4 inches thick or 2.25 sq ft at 2 inches.

How much does a yard of concrete weigh?

About 3,780 to 4,050 lb, based on 140–150 lb per cubic foot for normal-weight concrete.

Is it cheaper to buy ready-mix or mix bags yourself?

It depends on local prices and the size of the job. Multiply the bag count by the bag price, then compare it with the ready-mix price per yard plus any small-load and delivery fees. Remember that each cubic yard is 45 bags of 80 lb to mix by hand.

Related calculators

Sources

  1. National Ready Mixed Concrete Association, CIP 8: Discrepancies in Yield. Checked 2026-09-26.
  2. Sonoco, Sonotube Builder’s Tube concrete forms brochure (2016). Concrete per foot of tube by diameter. Checked 2026-09-26.
  3. QUIKRETE, Concrete Mix No. 1101 data sheet (rev. Oct 2022). Bag yields: 40 lb 0.30, 50 lb 0.375, 60 lb 0.45, 80 lb 0.60 cu ft; water per bag. Checked 2026-09-26.
  4. SAKRETE, High-Strength Concrete Mix technical data sheet. Bag yields match QUIKRETE at 40, 60 and 80 lb. Checked 2026-09-26.
  5. SAKRETE, Pro Tip: Estimating Bagged Concrete Jobs. 45 bags of 80 lb per cubic yard; add 10%. Checked 2026-09-26.
  6. National Ready Mixed Concrete Association, CIP 31: Ordering Ready Mixed Concrete. Truck capacity 8–12 cu yd; order 4–10% extra. Checked 2026-09-26.
  7. Kuert Concrete (ready-mix producer, Indiana), Do-It-Yourself Concrete Guide. Example short-load policy of one supplier. Checked 2026-09-26.
  8. QUIKRETE, Project sheet: Concrete Patios. Checked 2026-09-26.
  9. QUIKRETE, Project sheet: Concrete Sidewalks and Small Slabs. Checked 2026-09-26.
  10. QUIKRETE, Project sheet: Concrete Driveways and Curbs. Checked 2026-09-26.
  11. International Code Council, International Residential Code 2021, Section R506 Concrete Floors (on ground), via UpCodes. Minimum slab-on-ground thickness 3½ in. Checked 2026-09-26.
  12. Ohio Ready Mixed Concrete Association, Guidelines for Durable Driveways, Carports, Patios, Walks. Checked 2026-09-26.
  13. National Ready Mixed Concrete Association, CIP 36: Structural Lightweight Concrete. Normal concrete 140–150 lb/cu ft. Checked 2026-09-26.
  14. Federal Highway Administration, Lightweight Concrete Bridge Design Primer (FHWA-HIF-19-067, 2021). Typical normal-weight concrete 145 lb/cu ft. Checked 2026-09-26.
  15. QUIKRETE, Project sheet: Setting Posts. Hole 3× post width; depth 1/3 of post length. Checked 2026-09-26.
  16. National Ready Mixed Concrete Association, CIP 6: Joints in Concrete Slabs on Grade. Checked 2026-09-26.

Prepared by the Yard & Build editors. The formulas behind this calculator are checked against hand-worked answers every time the site is built. Bag yields and weights checked September 26, 2026.