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. Manufacturer effective coverage then determines whole purchase units.
2 × (length + width) × wall heightbase × height ÷ 2gross walls + gables − selected deductionsnet area × (1 + extra % ÷ 100)recommended ft² ÷ 100ceiling(recommended area ÷ 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 200 ft² per box, buy 7 boxes with 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 7 in exposure, course count rounds the normalized wall height divided by exposure upward. Area-based board quantity remains primary.
Use manufacturer installed coverage, not dimensions lost to overlap.
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.
Exposure is visible vertical coverage per course, not physical board width. Board coverage equals 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. 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.
A rectangular building uses twice length plus 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 exposure, rounded upward.
Recommended area divided by effective box coverage, rounded upward.
Yes, from user-entered trim length and purchasable piece length only.
No. Optional costs are material-only.