HardiePlank Siding Calculator

HardiePlank is the lap version of James Hardie's fiber cement line, and it's counted in boards. The single number that most affects your count is the reveal — the exposed height of each course. A wider reveal means fewer courses and fewer boards for the same wall; a tighter reveal means more. Once you fix the reveal and the plank length, coverage per board is set and the math falls out.

This calculator uses standard plank coverage by default and converts your net wall area into boards, then into boxes. Adjust the price and waste to match your job and profile.

We'd rather be transparent than falsely precise. The quantity math is deterministic and matches standard takeoff practice, so if your inputs are right, your squares and piece counts are right. Where real-world variation lives — coverage by profile, and installed cost by region and crew — we use typical published figures and present them as ranges. That makes this a strong planning number, not a binding quote; a contractor's field measure remains the final word.

One figure rarely tells the whole story. Confirm these points and your hardie plank siding estimate becomes an order you can actually place with confidence.

• Confirm coverage: the default coverage is a planning figure. Check the exact coverage printed on your product's box or spec sheet and adjust it if it differs, since even a small change moves the piece count on a big wall.
• Match the waste to your walls: keep 10% for a simple rectangular house, and raise it toward 15% for gables, dormers, bay windows and lots of angled cuts, because those details generate short offcuts you can't reuse.
• Account for accessories: starter strip, trim, inside and outside corners, flashing and fasteners are all part of a complete order, not an afterthought — the takeoff above estimates each so your material list is whole.
• Keep a spare: hold back a piece or a full box for future repairs, since profiles and colors get discontinued over time and an exact match years later is hard to find.
• Time your order: have material delivered close to the start date, stored flat and dry, so it isn't sitting exposed or getting damaged before the crew arrives.

Re-run the numbers above after any change and lean on the per-wall audit to verify each surface one at a time, so what you order matches what the wall actually needs rather than a rough guess. That small habit is the difference between one clean delivery and a mid-project trip back to the supplier.