External Cladding Calculator – Boards, Battens & Cost
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External Cladding Calculator
Estimate boards or packs across walls and gables, with optional battens, membrane, fixings, trims and job costs.
YOUR ESTIMATE
Your external cladding estimate
Net coverage, new purchases, supporting materials and clear optional costs.
Enter elevations and product coverage, then calculate.
Inputs changed. Calculate again to update your estimate.
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Connect cladding quantities to the wall assembly
Use the selected product’s effective coverage when estimating external cladding. Nominal board width, covered width and whole-board purchases are different figures; keep openings and the cutting allowance visible.
The insulation calculator can estimate a separately specified insulation layer. Use the membrane roll calculator only for a membrane covered by its stated scope and your supplied wall specification; it does not select the appropriate wall layer.
For a detached timber building, use the garden room planner to coordinate the complete schedule. Roofline boards belong in the fascia and soffit calculator. Transfer cladding quantities once if the complete-building estimate already contains that package.
MEASURE · COVER · ESTIMATE
External cladding calculator for boards, battens and project costs
This free external cladding calculator estimates board or pack quantities from the net area of your walls and gables. It uses effective fitted coverage, then adds your selected cutting allowance and deducts usable matching stock. Optional battens, counter-battens, breather membrane, fixings and profiles can be added without making them compulsory for a quick estimate.
The result separates the cladding itself from supporting materials and job costs. That helps you see which figures come from measurements and which depend on a chosen product or installation specification. The free printout includes quantities, costs and the calculation assumptions.
How to use the calculator
- Choose metres and millimetres, or feet and inches.
- Enter each rectangular elevation and any separate triangular gable.
- Deduct measured window and door areas where appropriate.
- Choose individual boards or manufacturer coverage per pack.
- Enter effective fitted coverage and a deliberate cutting or spare allowance.
- Enable only the supporting materials required by the chosen system.
- Add optional labour and other costs, then calculate and print.
Effective cover width is different from board width
A board’s nominal face width may include a lap, tongue or other part that does not add new visible wall coverage. Use the effective fitted exposure specified for the product. For example, a 3 m board with an effective cover width of 150 mm represents 0.45 m² of coverage. A 15 m² wall would need 34 such boards before any cutting allowance or owned stock adjustment.
That is an area estimate. It does not prove that 34 boards create a workable layout for a particular wall. Board length, course arrangement, supported end joints, stagger, defects and whether cut pieces can be reused all affect an actual order. A wall with many openings may need more cutting material than its net area suggests.
If the supplier sells a pack with a stated usable area, choose the pack method. Make sure the coverage describes the installed product, rather than a gross surface measurement that ignores overlaps. When changing between boards and packs, review the retained stock and price entries because they now refer to a different purchase unit.
Rectangular walls, triangular gables and openings
A rectangle uses width multiplied by height. A triangle uses half its base width multiplied by its perpendicular rise. Enter the rectangular wall below a gable as one section and the triangular area above it as another. This avoids counting the same area twice.
Openings deduct from each section before copies are applied. If two identical elevations each contain a 2 m² opening, enter a 2 m² deduction and two copies. Do not enter the combined deduction unless the row itself represents the combined area. The excluded area must be smaller than the section’s gross area.
For irregular shapes, split the work into non-overlapping rectangles and triangles, or use independently checked equivalent sections. The calculator does not infer the positions of openings. Net area alone cannot describe the short cuts around a window or the extra support and trim around its edges.
Choosing a cutting and spare allowance
The cladding allowance starts at zero so it remains an explicit choice. Set it after considering the product, board lengths and your elevation drawings. Gables, short returns, colour selection, damaged boards and difficult joint arrangements can all affect usable yield.
The calculation adds the allowance to net area, divides by coverage per board or pack and rounds up to whole purchases. It then subtracts matching whole boards or packs already available. Only count stock that is suitable for the same finish, dimensions and installation. Short offcuts should not be entered as complete boards.
Optional battens and counter-battens
The support-batten option offers a bounding-rectangle grid estimate or a measured total length. In grid mode, enter the specified support direction and centres. The number of supports is the across dimension divided by the centres, rounded up, plus an edge support. Their lengths use the full dimension along the supports.
For example, a 6 m-wide, 3 m-high wall with vertical supports at entered 0.6 m centres has 11 support lines and a 33 m baseline run. The 0.6 m value is an arithmetic example, not a recommended spacing. The actual system must specify appropriate supports and fixings.
The grid keeps full bounding rectangles and does not deduct openings. A triangular gable is also treated as its bounding rectangle for this estimate, so it can overstate its support length. Use measured mode when you have a detailed support plan. Add separately measured support lengths for joints, corners, opening edges and other details that the simple grid cannot locate.
Counter-battens have a separate optional measured run. Their quantity is not inferred from cladding orientation. The calculator does not design a drained cavity, choose timber dimensions or determine a suitable structural arrangement. Total-length purchasing also does not nest individual cuts; check long pieces, supported joins and offcut reuse before buying.
Membrane, fixings and profiles
Breather membrane can use gross elevation area before openings or net area after openings. Select the basis matching the actual installation plan. Enter usable coverage per roll and an overlap or cutting allowance consistently. If the roll coverage already accounts for all overlaps, adding the same allowance again would double count them.
Fixings use your specified rate per net area, with an optional spare percentage. The total rounds to whole fixings, usable matching stock is deducted, and purchases round to packs. This does not select a fixing type or assess loads. Board fixings, batten anchors and other connections can follow different schedules and should not be assumed interchangeable.
Starter or ventilation profiles, corner or edge profiles and opening trims each have their own optional measured run, stock length, allowance, owned stock and price. Use one compatible profile type within each category. Check actual details at starts, ends, windows and corners rather than assuming a simple wall perimeter describes every trim.
Building a clearer cladding job price
Cladding cost multiplies new whole boards or packs by the entered purchase price. Supporting materials are priced separately. Labour can use net clad area, hours or days, depending on how you estimate the work. Other costs can include independently assessed access, removal, disposal, coating or specialist details.
Keep all cost inputs on the same tax basis. Markup is added to total cost, then the entered VAT or sales tax is applied. Markup is different from profit margin. Currency selection changes the displayed symbol; it does not convert prices using an exchange rate.
Turning an optional checkbox off removes that material from the estimate while retaining its entries for later use. Collapsing a costs section keeps its values active. The input guidance makes this distinction visible so a hidden section is not mistaken for an excluded cost.
Frequently asked questions
Does this calculate a board cutting layout?
No. It calculates quantities from effective area coverage and your allowance. It does not place courses, nest offcuts or choose supported joint locations. Check the final board layout before ordering.
Can I include a triangular gable?
Yes. Enter its base and perpendicular rise as a triangle, separately from the wall beneath. The cladding area is triangular; the optional support grid uses its full bounding rectangle and labels that assumption.
Should I deduct every window and door?
Use measured deductions appropriate to the cladding area, then review the cutting allowance. Deductions do not automatically remove batten lengths or calculate opening trims because their positions and details are unknown.
Can I use nominal board width?
Use effective fitted cover width after laps or interlocks. If nominal width equals fitted coverage for your chosen system, they may be the same; confirm this from the product information.
Does the calculator choose support spacing?
No. You enter specified centres or a measured run. Support dimensions, anchors, cavity ventilation and installation details require the actual product and project design.
Are membrane, fixings and trims compulsory inputs?
No. They are optional estimating sections. Leaving them off gives a cladding-only result, but does not imply those materials are unnecessary for the actual installation.
Can I print the estimate for free?
Yes. Calculate and use Print / Save PDF. The estimate does not require an account, email address or purchase. The separate quote and invoice product is optional.
Product and design references
The TDCA cladding design guidance discusses the drained and ventilated cavity and other project considerations. Its cladding checklist covers product and installation planning. For proprietary systems, consult the actual manufacturer’s current details, such as the Hardie Plank product information. These references do not make different cladding systems interchangeable.