Concrete Cost Comparison Calculator

How it works

Both options start from the same volume with the waste allowance added. Bagged mix is that volume divided by the yield of one bag, rounded up to whole bags, times the bag price, plus the mixer rental. Ready-mix is the volume in cubic yards rounded up to the supplier's order increment, times the price per yard, plus the delivery charge, plus the short-load charge when the order is below the minimum.

Bag cost per cubic yard is the bag price times the bags in 27 cu ft (27 ÷ yield). When it is higher than the ready-mix price per yard, ready-mix gets relatively cheaper as the volume grows, and there is a volume above which it never costs more than bags: the break-even volume. When bags cost no more per yard, there is none.

Because both costs go up in steps (whole bags, quarter yards, the short-load charge switching off), the costs can cross more than once near the break-even point. The calculator checks every step in order and reports the volume, as entered before waste, above which ready-mix is never the dearer option.

Formula

with waste (cu ft) = volume (cu ft) × (1 + waste ÷ 100)
bagged             = ⌈ with waste ÷ yield ⌉ × bag price + mixer rental
ready-mix order    = ⌈ with waste ÷ 27 ÷ increment ⌉ × increment
ready-mix          = order × price per yd + delivery + [order < minimum] short-load charge
bag cost per yd    = bag price × 27 ÷ yield
break-even         = smallest volume above which ready-mix ≤ bagged at every volume
yield (cu ft): 40 lb 0.30 · 50 lb 0.375 · 60 lb 0.45 · 80 lb 0.60 · 90 lb 0.675 (QUIKRETE No. 1101, rev. Oct 2022)

Example

One cubic yard with 10% waste is 29.7 cu ft. In 80 lb bags at 0.60 cu ft that is 50 bags; at an illustrative $6.50 a bag plus $60 mixer rental, bagged mix costs $385. Ready-mix rounds 1.1 cu yd up to 1.25 cu yd; at $165 per yard plus a $100 short-load charge it costs $306.25. Ready-mix is lower by $78.75.

Bags at $6.50 for 0.60 cu ft cost $292.50 per cubic yard against $165 for ready-mix, so ready-mix stays cheaper as the volume grows. Checking every step, the last point at which ready-mix is dearer is 15 cu ft with waste (25 bags at $222.50 against 0.75 cu yd of ready-mix at $223.75); above it ready-mix never costs more. Before waste that is 15 ÷ 1.1 = 13.64 cu ft, a break-even volume of 0.51 cu yd.

Assumptions and limitations

• All prices are yours to enter; the defaults are illustrative and no live price data is used. Taxes, tool and form costs, labour, pumping and waiting time are not included.
• Bag yields are the approximate figures on the QUIKRETE Concrete Mix No. 1101 data sheet (revised October 2022): 0.30 cu ft per 40 lb bag, 0.375 per 50 lb, 0.45 per 60 lb, 0.60 per 80 lb and 0.675 per 90 lb. Other brands and mixes yield differently and the bag label governs.
• The same waste allowance applies to both options. Ready-mix is rounded up to the order increment and bags to whole bags, which is what each option actually sells.
• The short-load charge is one flat charge when the whole ready-mix order is below the minimum, and the delivery charge is one flat charge per order. Suppliers' terms differ; multi-truck delivery charges are not modelled.
• The break-even search stops at 2,000 cu yd with waste. Mixer rental is treated as one flat charge whatever the volume, although a large bagged pour may need a longer rental or more mixers.
• This is a cost comparison from the figures entered, not a quote and not engineering. Bagged and ready-mix concrete may differ in strength and in the mix a project specifies.

Frequently asked questions