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Slate Shingle Course Calculator

Calculate the number of slate shingle courses needed for a roof run, based on the slate's weather exposure.

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
19.69 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Slate courses needed

32 courses

High confidence

With the figures above, the slate courses needed comes to 32. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

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

  • Course count = ceil(roof run length ÷ slate exposure), the same course-layout method used for wood shingles, applied to slate's typical weather exposure

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Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Why does slate exposure matter for course count?
Slate courses are laid with each slate overlapping the one two courses below (headlap), leaving only the exposure portion visible to weather — a smaller exposure means more overlap and more courses to cover the same roof run.
How do I find the correct weather exposure for my slate?
Weather exposure depends on the slate's length and the required headlap for your roof's pitch — consult the slate manufacturer's exposure table, which sets exposure based on slate size and minimum headlap requirements.
Does this account for the starter course or hip/ridge slates?
No — this calculates the base number of regular field courses from eave to ridge. The starter course, ridge closure, and any hip or valley detailing should be planned separately.