Concrete Volume Calculator — ft, yd, bags
How to use this calculator
Pick a shape, enter dimensions in feet, inches, and fractions, then click Add Item to push it onto the takeoff list. Mix slabs, columns, walls, footings, sonotubes, and custom volumes in one pour schedule — the running total in cubic yards, cubic feet, and bags updates as you build the list.
Each item keeps its own shape, dimensions, and volume so you can delete or re-add to match field changes. Add a waste allowance (5–10% is typical, more for over-excavated subgrade) and enable Cost Estimate to price the job by ready-mix truck (per yd³), 80-lb bags, or 60-lb bags. For a single bagged pour, the concrete bag calculator is faster; for reinforced members size steel with the concrete beam and column calculators.
How to Use the Concrete Volume Calculator
Build a takeoff one element at a time: choose slab, column, wall, footing, sonotube, or a custom volume, enter feet/inches/fractions, then Add Item. The list keeps every member so you can price one continuous ready-mix order instead of guessing per element. Order in 0.25 yd³ increments — most ready-mix plants bill a short-load fee below about 3 yd³, which is why the cost panel lets you compare truck delivery against bagged mix for small pours.
Concrete Volume Formulas
Slab / footing / wall: Length × Width × Thickness (rectangular prism)
Round column / sonotube: π × (D/2)² × Height × Qty
Square column: Side × Side × Height × Qty
All dimensions reduce to feet, multiply for ft³, then ft³ ÷ 27 = yd³. Weight uses normal-weight concrete at 150 lb/ft³ (4,050 lb/yd³) per ACI 318-19; lightweight or grout mixes weigh less. The waste slider scales the net volume up before bag and truck counts are derived.
Bag Coverage & Field Notes
An 80-lb bag yields ≈0.60 ft³ (0.022 yd³); a 60-lb bag ≈0.45 ft³ (0.017 yd³); bag counts here round up because partial bags are not sold. Above roughly 1 yd³ ready-mix is usually cheaper and gives consistent strength. For reinforced beams and columns size the steel with the beam rebar calculator or column rebar calculator; for site work see the wall, curb & gutter, and stairs calculators.
FAQ
How much waste should I add? 5% for a formed slab on a level base, 10% for typical work, 15–20% for footings on rough or over-excavated subgrade where concrete slumps into the soil.
Can I mix shapes in one order? Yes — that is the point of the takeoff list; all items sum into one yd³ and bag total so you place a single ready-mix order.
Does this include rebar or formwork? No — this is plain volume. Reinforcement is sized in the linked column and beam calculators; volume here is unaffected by bar displacement (negligible at typical ratios).
On pour day
Three things estimators forget when calling the plant. Short-load fee — most ready-mix plants charge $80–150 if you order under ~3 yd³, so a 10×10 shed slab (≈1.25 yd³ at 4″) is usually cheaper in 80-lb bags. PSI grade — driveways, garage slabs and any freeze-thaw exposure need ≥4000 psi (ACI 318-19, Chapter 19); upgrading from a 3000 psi sidewalk mix adds roughly $5–15/yd³. Pump truck — backyard pours past 30 ft of hose, second-floor decks, or columns up walls need a line or boom pump, typically $700–1,200 minimum. Round the truck order to the next 0.25 yd³ and add a buffer item for thickened edges or over-excavated footings — concrete is cheaper than a second mixer trip.
