Estimate exterior siding for walls and gables with opening deductions, extra material, siding squares, purchase units, lap exposure, trim, and optional cost.
Rectangular walls use width times height. Whole buildings use perimeter times wall height. Gables use one-half base times height.
Openings are subtracted before the selected extra-material allowance is applied once. User-entered manufacturer effective coverage then determines whole purchase units.
2 × (length + width) × wall heightbase × height ÷ 2gross walls + gables − selected deductionsnet area × (1 + extra percentage ÷ 100)recommended ft² ÷ 100ceiling(recommended area ÷ user-entered effective coverage per unit)A 40 × 30 ft building with 9 ft walls has 1,260 ft² gross wall area. Subtracting 160 ft² and adding 10% gives 1,210 ft², or 12.1 siding squares. At the illustrative user-entered 200 ft² per box, the exact requirement is 6.05 boxes, so buy 7, providing 190 ft² above the recommendation.
A 30 ft by 8 ft triangular gable has 120 ft² area; two have 240 ft².
For a 20 × 9 ft wall with a user-entered 12 ft board length and 7 in exposure, 10% extra gives 198 ft². The area method needs about 28.2857 boards, so buy 29; the simple whole-board grid comparison shows 16 courses and 32 boards before cut reuse.
The initial 200 ft²-per-unit value is an editable example, not universal package coverage. Use manufacturer installed coverage, accounting for overlap where applicable.
Some installers reuse offcuts around small openings; deduct only openings appropriate to your plan.
Enter measured trim length because trim cannot be inferred reliably from wall area.
Box, panel, piece, and carton coverage varies by siding product and profile. The calculator uses the effective coverage you enter and rounds only the purchase-unit result upward.
Exposure is visible installed vertical coverage per course, not physical board width. Board coverage equals user-entered board length times effective exposure.
Course and simple whole-board layout are shown only for a single rectangular wall. Cuts, seams, openings, staggering, corners, and offcut reuse can change actual count.
One US siding square is 100 ft² for ordering purposes. This area convention does not mean a carton universally contains one or two squares. The calculator reports fractional squares without rounding them to whole squares.
Optional siding cost uses whole boxes, panels, or boards. Optional trim cost is separate. Labor, wrap, sheathing, insulation, fasteners, scaffolding, delivery, and taxes are excluded.
Calculate exterior wall and gable area, subtract chosen openings, add extra material, then divide by effective product coverage.
One siding square is 100 square feet for ordering purposes.
A rectangular building uses twice the sum of length and width, multiplied by wall height.
Multiply base by height and divide by two.
You choose; small-opening offcuts may sometimes be reused.
Project complexity and product instructions vary; use the editable allowance.
The visible installed vertical coverage of a lap board after overlap.
Wall height divided by user-entered exposure, rounded upward.
Recommended area divided by the selected product's effective box coverage, rounded upward. The initial coverage is only an editable example.
Yes, from user-entered trim length and purchasable piece length only.
No. Optional costs are material-only.
VSI documents wall and gable estimating and the 100 ft² siding-square convention. Manufacturer product documentation shows that cartons may contain different coverage, so CalcRocket requires editable product coverage.