Siding Square Footage Calculator
Calculate net siding area by subtracting windows, doors, and other openings from gross wall area. Add waste factor for accurate material ordering.
Fiber Cement Siding Calculator
Calculate fiber cement siding planks needed for your project. Estimates plank count from wall area, plank dimensions, and exposure settings.
sq ft
ft
in
in
%
Coverage per Plank⧉
7 sq ft
Planks (no waste)⧉
172
Planks to Order⧉
189
With 10% waste
Total Linear Feet⧉
2,268 LF
Weight per Plank⧉
20.6 lbs
Total Weight⧉
3,898 lbs
Planning notes, formulas, and examples
About the Fiber Cement Siding Calculator
Fiber cement siding (often known by the brand name HardiePlank) is one of the most durable siding materials available. Made from a mixture of Portland cement, cellulose fibers, and sand, it resists rot, insects, fire, and impact better than wood or vinyl.
This calculator determines the number of fiber cement planks needed based on your net wall area, the plank dimensions, and the exposure (the visible portion after overlapping). Standard HardiePlank comes in 12-foot lengths, with widths of 6.25", 7.25", 8.25", or 12" nominal, and typical exposures of 5", 6", 7", or 10.75" respectively.
Fiber cement is heavier than vinyl or wood siding (about 2.5 lbs per sq ft), so your order quantity affects delivery logistics and scaffolding planning. Accurate plank counts prevent costly extra deliveries of this heavy material.
When This Page Helps
Fiber cement planks are heavy and expensive. Over-ordering wastes money on non-returnable material; under-ordering delays the project and requires a separate delivery. This calculator gives you a precise plank count.
How to Use the Inputs
- Enter the net siding area (from the siding square footage calculator).
- Enter the plank length (typically 12 ft).
- Enter the plank exposure (visible portion after overlap).
- Enter a waste factor (10–15%).
- Review the plank count and total linear feet.
Formula used
Coverage per Plank = Plank Length × (Exposure / 12)
Planks = Net Area / Coverage per Plank
Order Planks = Planks × (1 + waste%/100)
Weight = Order Planks × Plank Length × (Nominal Width / 12) × 2.5 lbs/sqftExample Calculation
Result: 189 planks
Coverage per plank = 12 × (7/12) = 7.0 sq ft. Planks = 1,200 / 7.0 = 171.4 → 172. With 10% waste = 172 × 1.10 = 189 planks. Weight ≈ 189 × 12 × (8.25/12) × 2.5 ≈ 3,898 lbs.
Tips & Best Practices
- Always pre-prime cut edges with HardiePlank Touch-Up Kit (primer) to prevent moisture absorption.
- Fiber cement must be cut with shears, a circular saw with a fiber cement blade, or a scoring knife — never a standard wood blade.
- Allow 1/8" gap between planks and trim for caulking (don't butt-joint tight).
- Store planks flat on a level surface, off the ground, and protected from rain.
- Use hot-dipped galvanized or stainless steel nails/screws only.
- Install over a weather-resistant barrier (house wrap) per manufacturer requirements.
Fiber Cement vs. Other Siding Materials
Fiber cement combines the appearance of wood with the durability of masonry. It doesn't rot, warp, or attract insects like wood. It doesn't melt or crack like vinyl. It's fire-resistant (Class A fire rating) and withstands hail better than most materials. The trade-off is weight, cost, and installation complexity.
Installation Considerations
Fiber cement requires blind-nailing (nails hidden by the overlapping plank above) for the best appearance. Each plank is nailed 1" from the top edge into studs. Two-person installation is recommended due to the weight and length of 12-foot planks. Always follow the manufacturer's installation guide for warranty compliance.
Cost Planning
Fiber cement siding installed costs $6–12 per sq ft depending on the product, finish, and labor market. Material alone runs $1.50–3.50 per sq ft. ColorPlus pre-finished adds $0.50–1.00 per sq ft but eliminates painting costs. The total project cost typically falls between wood and engineered wood siding.
Sources & Methodology
Last updated:
Frequently Asked Questions
The most popular HardiePlank is the 8.25" wide plank installed at 7" exposure (giving 1.25" overlap). This mimics traditional 8-inch lap siding. Other options include 6.25" plank at 5" exposure and 12" plank at 10.75" exposure for a wider look.
Fiber cement weighs approximately 2.3–2.5 lbs per square foot. A single 12-ft × 8.25" plank weighs about 20–22 lbs. A full pallet of about 120 planks weighs over 2,500 lbs, requiring a forklift or boom truck for delivery.
Plan 10% waste for simple rectangular walls. Plan 12–15% for walls with many windows and gables. Unlike vinyl, fiber cement cut-offs can sometimes be reused on shorter runs, reducing actual waste to 7–8% for experienced installers.
HardiePlank comes in primed (requires two coats of paint) or ColorPlus (factory pre-finished with a 15-year color warranty). ColorPlus costs more but provides a superior factory finish that outlasts field-applied paint.
James Hardie does not recommend installing over existing siding. The old siding should be removed so the weather-resistant barrier can be inspected and replaced if necessary, and so the new siding has a flat, solid nailing surface.
Smooth fiber cement has a flat, modern appearance. Woodgrain (cedarmill) has a realistic cedar texture embossed into the surface. Both perform identically; the choice is purely aesthetic. Woodgrain hides minor imperfections better.
More in this topic
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House Wrap Calculator
Calculate house wrap (weather barrier) rolls needed for exterior walls. Estimates from gross wall area with overlap allowance for Tyvek, Typar, and similar products.