Curb & gutter volume

How it is calculated

V = length × [curb width × (curb height above gutter + gutter thickness) + gutter width excluding curb × gutter thickness].

Keep the full result when using it in another calculation. Results show up to three decimal places; very small positive results use scientific notation (for example, 1e-6). No extra material for waste is added.

Sketch the cross section before measuring

Measure the straight run length and draw the curb and gutter as two adjacent rectangles. The curb rectangle includes the gutter-thickness base beneath it. Measure curb height from the top of the gutter to the curb top; do not include the base in that field.

Measure gutter width from the curb’s outside face to the gutter’s outside edge. That width excludes the curb, so the shared base is counted once rather than once in each rectangle.

Add the two cross-sectional areas

For a 12 ft run, a 0.5 ft curb width, a 0.75 ft curb height above the gutter, a 1 ft gutter width, and a 0.25 ft gutter thickness, the cross section is 0.5 × (0.75 + 0.25) + 1 × 0.25 = 0.75 ft². Multiplying by 12 ft gives 9 ft³.

If the gutter is curved, sloped, or changes shape along the run, these rectangular areas no longer describe the full section. Do not use a straight, constant-section result for a curved alignment.

Before you use the result

• The gutter base extends beneath the curb. Curb height is measured above the top of the gutter. The curb’s total depth is that height plus the gutter thickness.
• Gutter width is measured from the side of the curb to the outside edge of the gutter. This keeps the concrete beneath the curb from being counted twice.
• The cross section must stay the same along the full length. Sloped faces, sloped gutters, rounded corners, and curved sections are not included.

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