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Concrete Mix Calculator
The job-site concrete calculator for cubic yards. Enter the length, width and thickness of your slab, patio, driveway, footing or pad and read the volume in cubic yards, the number of 60 lb or 80 lb bags, and a rough cost — updated on every keystroke, never submitted anywhere.
1 · Dimensions
Imperial: length and width in feet, thickness in inches.
2 · Options
3 · Your take-off
Cubic yards · bags · estimated costHow the concrete math works
One formula, three units, no surprises: volume in cubic feet divided by 27 is your concrete calculator cubic yards answer, and the bag count comes straight from the bag yield printed on the sack.
Length and width in feet (or meters), thickness in inches (or centimeters). One toggle keeps all three fields in the same system.
Thickness is converted to feet (4 in = 0.33 ft), then divided by 27 to convert cubic feet to cubic yards.
An 80 lb bag yields 0.60 cu ft and a 60 lb bag yields 0.45 cu ft. The count is always rounded up, then priced per bag.
Handy reference numbers
= 27 cu ft = 0.765 cu m — the unit ready-mix trucks are sold in.
of 80 lb concrete make one cubic yard; it takes 60 bags of 60 lb.
A 10 × 10 ft patio at 4 in needs 1.23 cu yd — about 56 bags of 80 lb.
FAQ
How many bags of concrete do I need?
Divide the volume in cubic feet by the bag yield: 0.60 cu ft for an 80 lb bag, 0.45 cu ft for a 60 lb bag, then round up. A 10 × 10 ft slab at 4 in is 40 cu ft, so 67 bags of 80 lb — or 89 bags of 60 lb.
How do I get cubic yards from feet and inches?
Multiply length × width × thickness in feet to get cubic feet, then divide by 27. A 12 × 10 ft slab at 4 in is 12 × 10 × 0.33 = 40 cu ft, and 40 ÷ 27 = 1.48 cu yd.
Should I add extra concrete for waste?
Yes — order about 10% extra. Spillage, uneven subgrade and over-excavation all eat into the pour, and you cannot add water to concrete that ran short. Use the 10% waste toggle to price that in.
Is it cheaper to mix bags or order a truck?
Bags win for small pours, roughly under one cubic yard. Past about 60–80 bags (about 1.5 cu yd) a ready-mix truck is usually cheaper and far less work, even with a short-load fee.
Does this concrete calculator handle metric?
Yes. Switch to Metric and enter length and width in meters with thickness in centimeters; the result is still shown in cubic yards, cubic feet and cubic meters so you can order either way.
What about rebar, mesh or a gravel base?
This tool is a concrete take-off only — reinforcement, formwork, base gravel and finishing are separate jobs. Add those quantities before you head to the store.