Concrete Curb Calculator

How it works

A curb is a constant cross-section run along a line, so its volume is the area of the cross-section times the length. A straight curb is one rectangle: width × height. A curb and gutter adds a second rectangle for the gutter pan beside the curb: gutter width × gutter thickness. The two rectangles share a base, so the exposed curb face above the gutter is the curb height less the gutter thickness; for a straight curb the face shown is the full height.

The profile is entered in inches, so the area comes out in square inches and is converted to square feet (144 sq in per sq ft). Multiplying by the length in feet gives cubic feet, which is converted to cubic yards at 27 cu ft per yard.

The waste allowance is added for the amount to order. The bag count divides the volume with waste by the yield of one bag and rounds up.

Formula

section (sq in) = curb width × curb height  [+ gutter width × gutter thickness]
curb face (in)  = curb height [− gutter thickness]
section (sq ft) = section (sq in) ÷ 144
volume (cu ft)  = section (sq ft) × length
volume (cu yd)  = volume (cu ft) ÷ 27
to order        = volume (cu yd) × (1 + waste ÷ 100)
bags            = ⌈ volume (cu ft) × (1 + waste ÷ 100) ÷ yield per bag ⌉
yield per bag: 40 lb ≈ 0.30, 60 lb ≈ 0.45, 80 lb ≈ 0.60 cu ft (QUIKRETE No. 1101, rev. Oct 2022)

Example

A curb 6 in wide and 12 in high with a 24 in gutter pan 6 in thick has a 12 − 6 = 6 in exposed face. Its section is 6 × 12 + 24 × 6 = 72 + 144 = 216 sq in, or 1.5 sq ft. Over 100 ft that is 150 cu ft, or 5.56 cu yd.

With 10% waste the amount to order is 6.11 cu yd. In 80 lb bags it is 150 × 1.1 ÷ 0.60 = 275 bags exactly.

Assumptions and limitations

• The profile is modelled as rectangles: the curb as width × full height and the gutter as width × thickness beside it. Battered (sloped) faces, rounded top edges, a gutter that slopes or thickens toward the curb, and a mountable or rolled curb shape are not modelled; enter average dimensions for those, or work the true section area out separately.
• The default dimensions are illustrative: a 6 in exposed curb face with a 24 in gutter, drawn as a 6 × 12 in curb beside a 24 × 6 in gutter. They are not taken from any agency's standard detail; curb and gutter profiles are set by the local agency's standard details, which vary, and the drawing for the job governs.
• The length is the total run, measured once. Transitions, driveway drop-outs, curb returns at corners and inlet structures are not modelled.
• 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, 0.45 per 60 lb and 0.60 per 80 lb. Other brands and mixes yield differently and the bag label governs.
• The waste allowance is a typical figure and is editable.
• This is a material estimate, not engineering and not a determination that a profile meets any agency standard or code.

Frequently asked questions