Estimate concrete for slabs, footings, round columns, tubes, steps and curbs in cubic yards, feet and meters, with 40, 60 or 80 lb bag counts and cost.
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Check your inputs—Complete valid inputs to calculate a current result.
m or ft
0.001 – 1,000,000,000 m or ft
m or ft
0.001 – 1,000,000,000 m or ft
cm or in
0.001 – 1,000,000,000 cm or in
pieces
1 – 100,000 pieces
%
0 – 100 %
m³ per bag
0.000001 – 10 m³ per bag
Concrete quantity including allowance
2.2000 m³
Cubic yards2.8775
Cubic feet77.6923
Whole bags to purchase184
Rectangular slab volume only; excludes footings, reinforcement, structural design and site suitability. Use your actual bag yield and ordering allowance.
How this was calculated
V = length × width × depthPut in your numbers: 5 m × 4 m × (10 cm ÷ 100)Answer: 2 m³
Order volume = volume × (1 + allowance/100)Put in your numbers: 2 m³ × (1 + 10/100)Answer: 2.2 m³
Cubic yards = m³ ÷ 0.764554857984Put in your numbers: 2.2 ÷ 0.764554857984Answer: 2.8775 yd³ (77.6923 ft³)
Bags = ⌈order volume ÷ yield per bag⌉Put in your numbers: ⌈2.2 m³ ÷ 0.012 m³⌉Answer: 184 bags
Formula and method
Convert slab dimensions to meters, then multiply length × width × thickness × (1 + allowance/100). Divide by bag yield and round up.
Worked example
A 5 m by 4 m slab, 10 cm thick, needs 2 m³ before allowance. With 10% extra it needs 2.2 m³, or 184 bags yielding 0.012 m³ each.
Volume formulas for each shape
Each shape is worked in the entered length unit, with thickness-type measurements divided by 12 (inches to feet) or 100 (centimeters to meters). The volume is then multiplied by the number of identical pieces and by 1 + allowance/100.
Slab or footing: V = length × width × thickness.
Circular slab: V = π/4 × diameter² × thickness.
Round column or hole: V = π/4 × diameter² × height.
Steps: V = width × run × rise × n(n + 1)/2, treating each step as a solid block resting on the ground.
Curb and gutter: V = length × [curb depth × (curb height + flag thickness) + gutter width × flag thickness].
Bags and cost
The 40, 60 and 80 lb presets use 0.30, 0.45 and 0.60 ft³ per bag, the yields QUIKRETE’s own calculator uses for its Concrete Mix. Other products yield differently, so the custom yield field stays the default. Cost can be priced per cubic yard or cubic meter of ready-mix, or per bag.
Worked example: steps
Three steps 4 ft wide, each with a 7 in rise and an 11 in run: 4 × (11 ÷ 12) × (7 ÷ 12) × 3 × 4 ÷ 2 = 12.83 ft³, or 0.475 yd³ before allowance. With the allowance set to 0%, at 0.60 ft³ per 80 lb bag that is 22 bags; the default 10% allowance raises it to 14.12 ft³ and 24 bags.
Frequently asked questions
Does this specify structural thickness?
No. Thickness is an input supplied by you or your designer. The tool calculates quantity, not structural suitability, reinforcement or foundations.
How many 80 lb bags make a cubic yard?
At the 0.60 ft³ yield QUIKRETE lists for its 80 lb Concrete Mix, one cubic yard (27 ft³) needs 45 bags before any allowance. Check the yield printed on your bag.
How is concrete for steps calculated?
Each step is treated as a solid block from the ground up, so step k is k rises tall. Summing over n steps gives width × run × rise × n(n + 1)/2.