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Roadway Crown Cross-Slope Calculator

Calculate the elevation drop from a roadway's centerline crown to its edge, for a target drainage cross-slope.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax
11.48 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Edge elevation drop

2.76 in

High confidence

For the dimensions entered, expect a edge elevation drop of 70 mm. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

Add the equipment this sizes

This result is a specification — 2.756 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Edge elevation drop = half-width × target cross-slope percentage, the standard method for establishing a roadway crown's drainage slope from centerline to edge of pavement

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Frequently asked questions

Why does a roadway need a crown cross-slope?
The cross-slope establishes the drainage grade from the centerline crown down to the edge of pavement, which the edge elevation drop calculation is based on.
What cross-slope percentage is typical?
2% is a commonly used target cross-slope for roadway drainage design, though your project's specific design standard may call for a different value.
How is the edge elevation drop calculated?
It's the half-width (the horizontal distance from centerline to edge of pavement) multiplied by the target cross-slope percentage — the standard method for setting a roadway crown's drainage slope from centerline to edge.