Redline
Free calculator

Yards for the pour, before you call the plant.

Length times width times thickness, turned into cubic yards, plus the extra you always order. Or the bag count, if it's a small pad you're mixing on site.

ft
ft
in
The thickness on your plans or spec. This tool only does volume.
%
Your call. Spillage, over-dig and form bulge all eat concrete.
cu ft
Printed on the bag. Only matters if you're mixing bags.
Volume66.7 cu ft
Cubic yards, exact2.47 cu yd
Cubic yards to order2.59 cu yd
Or bags, at the yield above117

Redline turns the yards into a quote line by chat, next to the base, the forms and the finish, with a deposit if you take one.

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How the math works

  1. Cubic feet

    Length x width x thickness, all in feet. 4 inches is 4 ÷ 12 = 0.333 ft, so 20 x 10 x 0.333 = 66.7 cu ft.

  2. Cubic yards

    A cubic yard is 27 cubic feet (3 x 3 x 3). 66.7 ÷ 27 = 2.47 yards.

  3. Your extra

    5% on top makes 2.59 yards. Set the percentage from your own pours.

  4. Or bags

    Cubic feet with the extra, divided by the yield printed on the bag, rounded up. 70 cu ft ÷ 0.6 = 116.7, so 117 bags.

Three example pours

5% extra, 0.6 cu ft per bag.

PourCubic feetCubic yardsWith 5% extraBags
10 x 10 pad, 4 in33.31.231.3059
20 x 10 patio, 4 in66.72.472.59117
24 x 24 slab, 5 in240.08.899.33420

The thicknesses are there for the arithmetic, not as recommendations. At 420 bags you'd be pricing ready-mix instead.

What to watch for

  • Volume only. This tool doesn't pick a thickness, a mix, rebar, mesh or a base. Those come from the plans, the engineer or your local code.
  • Thickened edges and footings hold concrete the rectangle doesn't see. Run each one as its own piece (the edge's length, its width, its extra depth) and add them up.
  • Subgrade is never flat. Check thickness in a few spots. Half an inch extra across a 600 sq ft driveway is close to another yard.
  • Ask the plant how it rounds. Ready-mix is ordered in fractions of a yard, and small loads may carry a fee. Your supplier sets those rules.
  • Bag yield is on the bag. Different bag weights and mixes yield different volumes. Type in the number on the one you're buying.

Questions contractors ask

How many cubic feet are in a yard of concrete?

27. A cubic yard is 3 ft by 3 ft by 3 ft.

How much extra should I order?

That's your call, and it depends on the forms, the grade and the crew. The calculator starts at 5% so you can see the effect. Change it to what your past pours tell you.

Can I use this for round footings or post holes?

Not this one; it's for rectangles. For round holes, use the fence post concrete calculator, which takes the diameter and subtracts the post.

How does Redline help once I have the yards?

Message the job the way you'd tell your foreman: "quote the Whitfields: 20 x 10 patio at 4 inches, 2.6 yards, gravel base, broom finish, 40% deposit." Redline drafts the itemized quote and saves it to their file. If rain moves the pour, "push the Whitfield pour to Thursday" moves it on the calendar. Billing the deposit and the balance with card pay links is on Solo and up. See concrete estimates.

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